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	<id>https://fire-safety.academy/w/index.php?action=history&amp;feed=atom&amp;title=Explosion</id>
	<title>Explosion - Revision history</title>
	<link rel="self" type="application/atom+xml" href="https://fire-safety.academy/w/index.php?action=history&amp;feed=atom&amp;title=Explosion"/>
	<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;action=history"/>
	<updated>2026-11-04T17:21:14Z</updated>
	<subtitle>Revision history for this page on the wiki</subtitle>
	<generator>MediaWiki 1.43.11</generator>
	<entry>
		<id>https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2853&amp;oldid=prev</id>
		<title>Jan: Remove links to pages that do not exist; retain displayed text (wiki-wide link audit).</title>
		<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2853&amp;oldid=prev"/>
		<updated>2026-11-02T21:32:49Z</updated>

		<summary type="html">&lt;p&gt;Remove links to pages that do not exist; retain displayed text (wiki-wide link audit).&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 22:32, 2 November 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l78&quot;&gt;Line 78:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 78:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Fireball]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Fireball]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Flammability limits]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Flammability limits]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;[[&lt;/del&gt;Hazardous area classification&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;]]&lt;/del&gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* Hazardous area classification&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Premixed flame]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Premixed flame]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Thermal runaway]]&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;* [[Thermal runaway]]&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;

&lt;!-- diff cache key firesb_pjbsiy42-wiki_:diff:1.41:old-2750:rev-2853:php=table --&gt;
&lt;/table&gt;</summary>
		<author><name>Jan</name></author>
	</entry>
	<entry>
		<id>https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2750&amp;oldid=prev</id>
		<title>Mark: Revise against the FSE wiki writing guidelines: abbreviation written out (revised by Claude Opus 5.5)</title>
		<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2750&amp;oldid=prev"/>
		<updated>2026-11-02T18:09:56Z</updated>

		<summary type="html">&lt;p&gt;Revise against the FSE wiki writing guidelines: abbreviation written out (revised by Claude Opus 5.5)&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
				&lt;col class=&quot;diff-marker&quot; /&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 19:09, 2 November 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l59&quot;&gt;Line 59:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 59:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Explosion protection interrupts the chain of events that leads to an explosion. It can prevent a flammable fuel-air mixture from forming, for example by ventilation or [[inerting]]. It can remove ignition sources, for example by earthing equipment so that static electricity cannot discharge as a spark. It can also limit the pressure rise by explosion venting or explosion suppression.&amp;lt;ref name=&amp;quot;Z402&amp;quot; /&amp;gt; Deflagration pressure containment instead designs a vessel and its fittings to withstand the maximum pressure of an internal deflagration.&amp;lt;ref name=&amp;quot;IS-F20&amp;quot; /&amp;gt; In the United States, Factory Mutual Data Sheet 7-32 (1993 edition) recommends at least one of four protections for process equipment that could explode: venting, enough strength to resist the overpressure, inerting or suppression.&amp;lt;ref name=&amp;quot;IS-B27&amp;quot;&amp;gt;Iqbal and Salley (2004), pp. B-27–B-28.&amp;lt;/ref&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Explosion protection interrupts the chain of events that leads to an explosion. It can prevent a flammable fuel-air mixture from forming, for example by ventilation or [[inerting]]. It can remove ignition sources, for example by earthing equipment so that static electricity cannot discharge as a spark. It can also limit the pressure rise by explosion venting or explosion suppression.&amp;lt;ref name=&amp;quot;Z402&amp;quot; /&amp;gt; Deflagration pressure containment instead designs a vessel and its fittings to withstand the maximum pressure of an internal deflagration.&amp;lt;ref name=&amp;quot;IS-F20&amp;quot; /&amp;gt; In the United States, Factory Mutual Data Sheet 7-32 (1993 edition) recommends at least one of four protections for process equipment that could explode: venting, enough strength to resist the overpressure, inerting or suppression.&amp;lt;ref name=&amp;quot;IS-B27&amp;quot;&amp;gt;Iqbal and Salley (2004), pp. B-27–B-28.&amp;lt;/ref&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;−&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Inerting adds a gas such as nitrogen or carbon dioxide to reduce the oxygen concentration to a safe level&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;. The &lt;/del&gt;highest &lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;safe level &lt;/del&gt;is called the limiting oxidant concentration.&amp;lt;ref name=&quot;Z402&quot; /&amp;gt;&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; For the flammable gases and vapours listed by Zalosh, apart from hydrogen, this limit is 9.5 to 12 per cent oxygen by volume with nitrogen. With carbon dioxide it is 11.5 to 14.5 per cent, while hydrogen needs about 5 per cent with either gas.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; In the United States, NFPA 69 (1997 edition) states that oxygen should be kept at least 2 percentage points below this limit under continuous monitoring&lt;del style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;, and further below it otherwise&lt;/del&gt;.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; Uneven mixtures and the accuracy and response time of oxygen monitors also have to be considered.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Inerting adds a gas such as nitrogen or carbon dioxide to reduce the oxygen concentration to a safe level&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;, the &lt;/ins&gt;highest &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;of which &lt;/ins&gt;is called the limiting oxidant concentration.&amp;lt;ref name=&quot;Z402&quot; /&amp;gt;&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; For the flammable gases and vapours listed by Zalosh, apart from hydrogen, this limit is 9.5 to 12 per cent oxygen by volume with nitrogen. With carbon dioxide it is 11.5 to 14.5 per cent, while hydrogen needs about 5 per cent with either gas.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; In the United States, &lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;the National Fire Protection Association standard &lt;/ins&gt;NFPA 69 (1997 edition) states that oxygen should be kept at least 2 percentage points below this limit under continuous monitoring&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;. Without such monitoring a larger margin is needed&lt;/ins&gt;.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt; Uneven mixtures and the accuracy and response time of oxygen monitors also have to be considered.&amp;lt;ref name=&quot;Z403&quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;[[Explosion venting]] releases the combustion gases through openings during a deflagration, so that the pressure stays below the level that would damage the enclosure.&amp;lt;ref name=&amp;quot;Z414&amp;quot;&amp;gt;Zalosh (2002), p. 3-414.&amp;lt;/ref&amp;gt; The openings are usually covered by blow-off panels, rupture discs or other vent devices, which usually open only after ignition. Venting works best when the vents open early, are as large as possible and let the gases escape freely. In the outside walls and roofs of buildings, the lowest practical opening pressure is usually just above the highest expected wind pressure, typically 0.96 to 1.44 kPa.&amp;lt;ref name=&amp;quot;Z414&amp;quot; /&amp;gt; Explosion suppression instead detects an explosion in its first moments and discharges an extinguishing agent that quenches the flame.&amp;lt;ref name=&amp;quot;Z417&amp;quot;&amp;gt;Zalosh (2002), p. 3-417.&amp;lt;/ref&amp;gt; It releases no flame or fuel, so it suits indoor equipment and toxic materials, but it is expensive to install and to reset.&amp;lt;ref name=&amp;quot;Z417&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;[[Explosion venting]] releases the combustion gases through openings during a deflagration, so that the pressure stays below the level that would damage the enclosure.&amp;lt;ref name=&amp;quot;Z414&amp;quot;&amp;gt;Zalosh (2002), p. 3-414.&amp;lt;/ref&amp;gt; The openings are usually covered by blow-off panels, rupture discs or other vent devices, which usually open only after ignition. Venting works best when the vents open early, are as large as possible and let the gases escape freely. In the outside walls and roofs of buildings, the lowest practical opening pressure is usually just above the highest expected wind pressure, typically 0.96 to 1.44 kPa.&amp;lt;ref name=&amp;quot;Z414&amp;quot; /&amp;gt; Explosion suppression instead detects an explosion in its first moments and discharges an extinguishing agent that quenches the flame.&amp;lt;ref name=&amp;quot;Z417&amp;quot;&amp;gt;Zalosh (2002), p. 3-417.&amp;lt;/ref&amp;gt; It releases no flame or fuel, so it suits indoor equipment and toxic materials, but it is expensive to install and to reset.&amp;lt;ref name=&amp;quot;Z417&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;

&lt;!-- diff cache key firesb_pjbsiy42-wiki_:diff:1.41:old-2683:rev-2750:php=table --&gt;
&lt;/table&gt;</summary>
		<author><name>Mark</name></author>
	</entry>
	<entry>
		<id>https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2683&amp;oldid=prev</id>
		<title>Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, added sources, structure, links, See also, style (revised by Claude Opus 5.5)</title>
		<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=2683&amp;oldid=prev"/>
		<updated>2026-11-02T17:52:13Z</updated>

		<summary type="html">&lt;p&gt;Revise against the FSE wiki writing guidelines: verified and corrected citations, added sources, structure, links, See also, style (revised by Claude Opus 5.5)&lt;/p&gt;
&lt;a href=&quot;https://fire-safety.academy/w/index.php?title=Explosion&amp;amp;diff=2683&amp;amp;oldid=1144&quot;&gt;Show changes&lt;/a&gt;</summary>
		<author><name>Mark</name></author>
	</entry>
	<entry>
		<id>https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=1144&amp;oldid=prev</id>
		<title>Sanne: Add diagrams fse-explosion-v1.svg, fse-explosion-v2.svg, fse-explosion-v3.svg (level-1 visual plan)</title>
		<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=1144&amp;oldid=prev"/>
		<updated>2026-11-02T07:22:39Z</updated>

		<summary type="html">&lt;p&gt;Add diagrams fse-explosion-v1.svg, fse-explosion-v2.svg, fse-explosion-v3.svg (level-1 visual plan)&lt;/p&gt;
&lt;table style=&quot;background-color: #fff; color: #202122;&quot; data-mw=&quot;interface&quot;&gt;
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				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;← Older revision&lt;/td&gt;
				&lt;td colspan=&quot;2&quot; style=&quot;background-color: #fff; color: #202122; text-align: center;&quot;&gt;Revision as of 08:22, 2 November 2026&lt;/td&gt;
				&lt;/tr&gt;&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l26&quot;&gt;Line 26:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 26:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A quasi-detonation describes a situation where flame speed is slightly below sound speed but pressure is nonuniform without a detonation shock wave. This illustrates why pressure distribution matters in addition to the speed label. The physical evidence should determine the design case.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A quasi-detonation describes a situation where flame speed is slightly below sound speed but pressure is nonuniform without a detonation shock wave. This illustrates why pressure distribution matters in addition to the speed label. The physical evidence should determine the design case.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;[[File:fse-explosion-v1.svg|thumb|upright=1.5|alt=Deflagration fills a vessel over time; detonation produces a sharp local shock front.|Deflagration and detonation create different pressure conditions. Based on Zalosh (2002), pp. 3-411–3-412 and U.S. Nuclear Regulatory Commission (2005), pp. F-20–F-21.]]&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Deflagration-to-detonation transition must be considered where geometry and flame acceleration make it credible. Zalosh distinguishes the need to assess this possibility before choosing a protection method. A system designed only for an initial deflagration may not remain adequate after transition.&amp;lt;ref name=&amp;quot;Zalosh-3-412&amp;quot;&amp;gt;Zalosh (2002), pp. 3-412–3-413.&amp;lt;/ref&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Deflagration-to-detonation transition must be considered where geometry and flame acceleration make it credible. Zalosh distinguishes the need to assess this possibility before choosing a protection method. A system designed only for an initial deflagration may not remain adequate after transition.&amp;lt;ref name=&amp;quot;Zalosh-3-412&amp;quot;&amp;gt;Zalosh (2002), pp. 3-412–3-413.&amp;lt;/ref&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l56&quot;&gt;Line 56:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 57:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A vessel can fail from impact, corrosion, internal overheating, manufacturing defects or other weakening mechanisms. NUREG-1805 explains that the unwetted internal surface is particularly exposed to fire heating because it lacks the liquid&amp;#039;s heat absorption. The physical condition of the vessel must therefore be part of the scenario.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A vessel can fail from impact, corrosion, internal overheating, manufacturing defects or other weakening mechanisms. NUREG-1805 explains that the unwetted internal surface is particularly exposed to fire heating because it lacks the liquid&amp;#039;s heat absorption. The physical condition of the vessel must therefore be part of the scenario.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;[[File:fse-explosion-v2.svg|thumb|upright=1.5|alt=Heated vessel fails, releasing expanding vapour, fragments, blast and a fireball.|A BLEVE combines physical expansion with several possible hazards. Based on U.S. Nuclear Regulatory Commission (2005), pp. 5-15–5-16 and Zalosh (2002), p. 3-420.]]&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A BLEVE can produce a large fireball and intense radiant heat when the released contents ignite. The fireball is a separate hazard from blast and vessel fragments. Assessment should consider fuel mass, fireball size, duration, radiation and fragment trajectories.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;A BLEVE can produce a large fireball and intense radiant heat when the released contents ignite. The fireball is a separate hazard from blast and vessel fragments. Assessment should consider fuel mass, fireball size, duration, radiation and fragment trajectories.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot; id=&quot;mw-diff-left-l82&quot;&gt;Line 82:&lt;/td&gt;
&lt;td colspan=&quot;2&quot; class=&quot;diff-lineno&quot;&gt;Line 84:&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Suppression detects and arrests combustion while it remains incipient. Containment instead specifies an enclosure able to withstand the expected deflagration pressure. These approaches act differently and should not be presented as substitutes for every explosion scenario.&amp;lt;ref name=&amp;quot;NUREG-F20&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Suppression detects and arrests combustion while it remains incipient. Containment instead specifies an enclosure able to withstand the expected deflagration pressure. These approaches act differently and should not be presented as substitutes for every explosion scenario.&amp;lt;ref name=&amp;quot;NUREG-F20&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td colspan=&quot;2&quot; class=&quot;diff-side-deleted&quot;&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot; data-marker=&quot;+&quot;&gt;&lt;/td&gt;&lt;td style=&quot;color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;&lt;ins style=&quot;font-weight: bold; text-decoration: none;&quot;&gt;[[File:fse-explosion-v3.svg|thumb|upright=1.5|alt=Prevention, venting and containment are mapped to deflagration; venting is excluded for detonation.|Protection must match the explosion mechanism. Based on Zalosh (2002), pp. 3-411–3-416.]]&lt;/ins&gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;br&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Explosion venting and many suppression methods are unsuitable for detonation. The local shock reaches a point too quickly for a developing pressure rise to be relieved in time. Protection must therefore begin with the correct deflagration-versus-detonation assessment.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;td class=&quot;diff-marker&quot;&gt;&lt;/td&gt;&lt;td style=&quot;background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;&quot;&gt;&lt;div&gt;Explosion venting and many suppression methods are unsuitable for detonation. The local shock reaches a point too quickly for a developing pressure rise to be relieved in time. Protection must therefore begin with the correct deflagration-versus-detonation assessment.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;/div&gt;&lt;/td&gt;&lt;/tr&gt;

&lt;!-- diff cache key firesb_pjbsiy42-wiki_:diff:1.41:old-722:rev-1144:php=table --&gt;
&lt;/table&gt;</summary>
		<author><name>Sanne</name></author>
	</entry>
	<entry>
		<id>https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=722&amp;oldid=prev</id>
		<title>Jan: New FSE wiki article: Explosion (written by Kimi Code CLI)</title>
		<link rel="alternate" type="text/html" href="https://fire-safety.academy/w/index.php?title=Explosion&amp;diff=722&amp;oldid=prev"/>
		<updated>2026-11-02T03:28:21Z</updated>

		<summary type="html">&lt;p&gt;New FSE wiki article: Explosion (written by Kimi Code CLI)&lt;/p&gt;
&lt;p&gt;&lt;b&gt;New page&lt;/b&gt;&lt;/p&gt;&lt;div&gt;An &amp;#039;&amp;#039;&amp;#039;Explosion&amp;#039;&amp;#039;&amp;#039; is a sudden, violent expansion or production of gases that can be accompanied by heat, shock waves and disruption of nearby structural materials. Combustion explosions involve rapid reaction in a fuel-oxidant mixture, while other explosions can involve physical expansion and vessel failure. The resulting hazard depends on pressure development, flame, fragments and the surrounding geometry.&amp;lt;ref name=&amp;quot;NUREG-F22&amp;quot;&amp;gt;U.S. Nuclear Regulatory Commission (2005), p. F-22.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot;&amp;gt;Zalosh (2002), pp. 3-402–3-403.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
A deflagration propagates combustion at subsonic speed, whereas a detonation propagates it at supersonic speed through the unreacted medium. This distinction changes both the pressure distribution and suitable protection. It is therefore not enough to classify an event only as an explosion without identifying its mechanism.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot;&amp;gt;Zalosh (2002), pp. 3-411–3-412.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;NUREG-F21&amp;quot;&amp;gt;U.S. Nuclear Regulatory Commission (2005), p. F-21.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Explosion assessment examines the formation of a hazardous condition, initiation, pressure or energy release and consequences. Protection can prevent flammable mixtures, control ignition, limit pressure or strengthen enclosures. Each measure has its own application limits and must be based on the relevant test and structural evidence.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot;&amp;gt;Zalosh (2002), pp. 3-414–3-416.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== Combustion and pressure development ==&lt;br /&gt;
&lt;br /&gt;
Combustible gases, vapours and dusts can form an explosion hazard when mixed with an oxidant between flammable limits and confined before ignition. Flame then propagates through the premixed fuel and oxidant. Restricted expansion of the hot combustion products produces a potentially damaging pressure rise.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Flammability-limit tests determine whether flame propagates through a known mixture. Explosibility-limit tests instead focus on overpressure, and the two criteria need not produce identical values. The selected test must match whether the objective is flame prevention or pressure-hazard evaluation.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Nonuniform mixtures can create local flammable regions even where the average concentration appears safe. Temperature, pressure and monitoring response can also change the relevant limits. A single room-average gas reading does not necessarily describe every region or time in the scenario.&amp;lt;ref name=&amp;quot;Zalosh-3-403&amp;quot;&amp;gt;Zalosh (2002), p. 3-403.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
In a closed vessel deflagration, pressure depends on flame propagation, burned-gas temperature and composition, and heat losses. Complete reaction throughout the enclosure is a particular idealisation, not a description of every real event. Near-limit mixtures can react incompletely and lose heat to walls.&amp;lt;ref name=&amp;quot;Zalosh-3-406&amp;quot;&amp;gt;Zalosh (2002), pp. 3-406–3-407.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Structural response depends on the pressure-time history and enclosure behaviour. A slowly developing pressure rise and a shock wave of short duration present different loads. Evaluation must therefore consider both the maximum pressure and how quickly it develops.&amp;lt;ref name=&amp;quot;Zalosh-3-410&amp;quot;&amp;gt;Zalosh (2002), pp. 3-409–3-412.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== Deflagration and detonation ==&lt;br /&gt;
&lt;br /&gt;
[[Deflagration]] is thermal propagation of an explosion reaction at less than the speed of sound in the mixture. Pressure can develop throughout an enclosure as the flame expands. Although slower than detonation, it can still rupture vessels and buildings.&amp;lt;ref name=&amp;quot;NUREG-F20&amp;quot;&amp;gt;U.S. Nuclear Regulatory Commission (2005), p. F-20.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-406&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
[[Detonation]] is propagation of a combustion zone at supersonic speed through the unreacted medium. Its pressure rise is highly nonuniform and occurs almost instantaneously as the shock front reaches a location. This is physically different from the distributed development of a closed-vessel deflagration.&amp;lt;ref name=&amp;quot;NUREG-F21&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Deflagration pressures can be moderated by early venting or suppression during the developing event. Detonation leaves no comparable period for those systems to respond at a downstream point. Its impulsive load requires different structural analysis and protection.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
A quasi-detonation describes a situation where flame speed is slightly below sound speed but pressure is nonuniform without a detonation shock wave. This illustrates why pressure distribution matters in addition to the speed label. The physical evidence should determine the design case.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Deflagration-to-detonation transition must be considered where geometry and flame acceleration make it credible. Zalosh distinguishes the need to assess this possibility before choosing a protection method. A system designed only for an initial deflagration may not remain adequate after transition.&amp;lt;ref name=&amp;quot;Zalosh-3-412&amp;quot;&amp;gt;Zalosh (2002), pp. 3-412–3-413.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== Dust explosions and secondary events ==&lt;br /&gt;
&lt;br /&gt;
[[Dust explosion]] occurs when combustible particles suspended in air ignite and burn rapidly, producing heat and pressure. Particle size, concentration, turbulence and ignition conditions determine whether propagation occurs. Confinement can make the consequences substantially more severe.&amp;lt;ref name=&amp;quot;Zalosh-3-403&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Dust requires dispersion before or during the event. Air injection, vibration and process disturbances can create clouds, while settled layers can be lifted by an earlier explosion. The assessment must include both the initial cloud and accumulated material that could feed a later one.&amp;lt;ref name=&amp;quot;Zalosh-3-404&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-410&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Secondary explosions arise when a primary event breaches equipment and disturbs surrounding dust. The blast and airflow suspend the dust, which can then ignite in the larger building. This sequence can produce casualties and structural damage beyond the original process enclosure.&amp;lt;ref name=&amp;quot;Zalosh-3-410&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Dust explosion tests report maximum pressure and size-normalised rate-of-pressure-rise parameters under specified conditions. These results support comparison and vent design, but they depend on ignition source, dispersion delay and vessel geometry. They should not be used as context-free material constants.&amp;lt;ref name=&amp;quot;Zalosh-3-410&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-415&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
== Vapour cloud explosions ==&lt;br /&gt;
&lt;br /&gt;
A [[Vapour cloud explosion]] involves ignition of a large flammable cloud with blast overpressure. Zalosh highlights highly obstructed chemical and petrochemical environments, where flame acceleration and confinement strongly affect blast strength. The term should not be applied to every cloud fire.&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot;&amp;gt;Zalosh (2002), pp. 3-420–3-421.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;Barry-5-184&amp;quot;&amp;gt;Barry (2002), pp. 5-184–5-185.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&lt;br /&gt;
A flash fire can burn rapidly through the flammable zone without producing the same blast damage. Barry distinguishes that outcome from an unconfined vapour cloud explosion, which creates explosion overpressure around the area. Flame presence alone does not establish which consequence model applies.&amp;lt;ref name=&amp;quot;Barry-5-184&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Blast strength depends on flame speed and confinement around the cloud. Obstacles and equipment can accelerate flame and change the pressure field. A model based only on total cloud energy can miss those near-field effects.&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Zalosh explains that early ideal-blast estimates were inaccurate for vapour cloud explosions, particularly because real blast strength and impulse did not decay like an ideal point-source blast. Newer approaches use flame-speed estimates, nonideal propagation calculations or computational fluid dynamics. Their suitability depends on scenario knowledge and user competence.&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
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Release size, duration and isolation influence the cloud that can develop. Barry&amp;#039;s discussion calls for realistic evaluation of detection and shutdown timing. Consequence assessment therefore begins before ignition, with the release and dispersion scenario.&amp;lt;ref name=&amp;quot;Barry-5-184&amp;quot; /&amp;gt;&lt;br /&gt;
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== BLEVE and vessel failure ==&lt;br /&gt;
&lt;br /&gt;
[[BLEVE]] stands for boiling liquid expanding vapour explosion. It involves sudden expansion of a liquid into gas when a pressurised vessel fails, with energy that can create a blast wave. The NFPA definition quoted by NUREG-1805 concerns failure of a major container while its liquid is above its normal-atmospheric boiling point.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot;&amp;gt;U.S. Nuclear Regulatory Commission (2005), pp. 5-15–5-16.&amp;lt;/ref&amp;gt;&lt;br /&gt;
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A vessel can fail from impact, corrosion, internal overheating, manufacturing defects or other weakening mechanisms. NUREG-1805 explains that the unwetted internal surface is particularly exposed to fire heating because it lacks the liquid&amp;#039;s heat absorption. The physical condition of the vessel must therefore be part of the scenario.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&lt;br /&gt;
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A BLEVE can produce a large fireball and intense radiant heat when the released contents ignite. The fireball is a separate hazard from blast and vessel fragments. Assessment should consider fuel mass, fireball size, duration, radiation and fragment trajectories.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
Not every BLEVE is simply a combustion deflagration inside a vessel. The initial phase change and vessel rupture are central to its mechanism. Subsequent fire and thermal radiation may then expose nearby people and property.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Barry-5-184&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
The source notes that many BLEVEs involve containers less than half to completely full, but this is a general observation from the cited NUREG section, not a design rule. It should not be used to infer that another fill condition is safe.&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&lt;br /&gt;
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== Smoke explosion ==&lt;br /&gt;
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A [[Smoke explosion]] involves very rapid combustion of gases formed by thermal decomposition or incomplete combustion. Van Rossum describes a typical requirement for air and pyrolysis gases to be reasonably premixed and within the lower and upper explosion limits. An ignition source or autoignition can initiate the event.&amp;lt;ref name=&amp;quot;VR-4-10&amp;quot;&amp;gt;Van Rossum (2027), §4.10.&amp;lt;/ref&amp;gt;&lt;br /&gt;
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Oxygen-limited combustion can allow unburned pyrolysis gases to accumulate. If air later mixes with those gases, a flammable cloud can form. The mixture then requires suitable temperature or another ignition source before rapid combustion occurs.&amp;lt;ref name=&amp;quot;VR-4-8&amp;quot;&amp;gt;Van Rossum (2027), §4.8.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;VR-4-10&amp;quot; /&amp;gt;&lt;br /&gt;
&lt;br /&gt;
This differs from a backdraft, which Van Rossum defines as explosive ignition of pyrolysis gases when oxygen suddenly enters a room. The two phenomena are related to ventilation and unburned gases, but they should not be treated as identical labels for every rapid smoke ignition.&amp;lt;ref name=&amp;quot;VR-4-9&amp;quot;&amp;gt;Van Rossum (2027), §4.9.&amp;lt;/ref&amp;gt;&amp;lt;ref name=&amp;quot;VR-4-10&amp;quot; /&amp;gt;&lt;br /&gt;
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Smoke explosion assessment must therefore include mixture history. It is not sufficient to ask whether a flame is currently visible. Fuel decomposition, oxygen depletion, gas accumulation and later mixing can establish the conditions for a later explosion.&amp;lt;ref name=&amp;quot;VR-4-8&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;VR-4-10&amp;quot; /&amp;gt;&lt;br /&gt;
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== Explosion protection ==&lt;br /&gt;
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Protection can interrupt the sequence before ignition. Ventilation or inerting can prevent a flammable mixture, while elimination of ignition sources can stop initiation. These measures should address actual process and environmental conditions rather than generic fuel names alone.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;br /&gt;
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Inerting reduces oxygen below the limiting concentration required for combustion. The necessary concentration depends on the fuel, inert gas and process conditions. Monitoring accuracy, nonuniformity and response time must be included in its reliability assessment.&amp;lt;ref name=&amp;quot;Zalosh-3-403&amp;quot; /&amp;gt;&lt;br /&gt;
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[[Explosion venting]] discharges gases during a deflagration to keep pressure below the enclosure damage threshold. It uses engineered openings that deploy after initiation. Early opening and unrestricted discharge are central to the cited performance, but required area depends on the enclosure and mixture.&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;br /&gt;
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Suppression detects and arrests combustion while it remains incipient. Containment instead specifies an enclosure able to withstand the expected deflagration pressure. These approaches act differently and should not be presented as substitutes for every explosion scenario.&amp;lt;ref name=&amp;quot;NUREG-F20&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&lt;br /&gt;
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Explosion venting and many suppression methods are unsuitable for detonation. The local shock reaches a point too quickly for a developing pressure rise to be relieved in time. Protection must therefore begin with the correct deflagration-versus-detonation assessment.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;br /&gt;
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== Testing, modelling and uncertainty ==&lt;br /&gt;
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Explosion tests establish flammability, pressure and rate-of-pressure-rise parameters under defined conditions. Vessel size, ignition strength, turbulence and geometry influence results. Those conditions must accompany any value used in a design or comparison.&amp;lt;ref name=&amp;quot;Zalosh-3-404&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-415&amp;quot; /&amp;gt;&lt;br /&gt;
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Vented-explosion models add vent area, deployment pressure and vent-device behaviour. They also need to represent enclosure scale, flame acceleration and equipment obstruction. A correlation developed from one test programme should not be applied to an unrelated geometry without justification.&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-416&amp;quot;&amp;gt;Zalosh (2002), pp. 3-415–3-417.&amp;lt;/ref&amp;gt;&lt;br /&gt;
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Computational fluid dynamics can represent spatial variation in gas velocity, composition and thermal properties. Zalosh notes that these models are more complicated than two-fluid approaches and are used for special applications. Their added detail does not remove the need for suitable input data and validation.&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;br /&gt;
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Blast and structural assessment must consider reflected waves, impulse and fragment hazards where relevant. A single peak-pressure number does not capture all those effects. The selected model should correspond to the physical event and the structural question.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
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Risk assessment combines frequency and consequence, but both are scenario dependent. Barry describes its use for prevention, protection and emergency planning. An explosion model&amp;#039;s output becomes useful for decisions only when its scenario, limitations and exposed targets are explicit.&amp;lt;ref name=&amp;quot;Barry-5-176&amp;quot;&amp;gt;Barry (2002), pp. 5-176–5-177.&amp;lt;/ref&amp;gt;&lt;br /&gt;
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Explosion scenarios should include the period before the hazardous mixture forms. Fuel storage, release rate, dispersion and isolation determine how much material can participate and where it travels. Limiting a release can change the scenario before ignition-control or pressure-relief measures are needed.&amp;lt;ref name=&amp;quot;Barry-5-184&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
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Mixture evidence should be interpreted by location and time. A cloud that is below a flammability limit at one point may be within it elsewhere, and continued release can change the average. The assessment should not treat a single sensor value as a complete description of a developing cloud.&amp;lt;ref name=&amp;quot;Zalosh-3-403&amp;quot; /&amp;gt;&lt;br /&gt;
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Fuel form changes the relevant test and model. Gas, vapour, dust and pressurised liquefied gas have different dispersion and energy-release processes. Their scenarios should not be combined merely because all can produce an explosion.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;NUREG-5-15&amp;quot; /&amp;gt;&lt;br /&gt;
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Structural assessment should retain the difference between pressure resistance and dynamic response. An enclosure may be designed for a specified deflagration pressure, but a detonation creates a different impulse and spatial load. Fragments and reflected waves can also create hazards beyond the enclosure.&amp;lt;ref name=&amp;quot;Zalosh-3-411&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-420&amp;quot; /&amp;gt;&lt;br /&gt;
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Operational controls should preserve the protection assumptions. Vent openings must remain available, inerting systems need suitable monitoring, and process changes can alter dust or vapour formation. A protection measure that exists on a drawing may not be effective after an alteration or impairment.&amp;lt;ref name=&amp;quot;Zalosh-3-403&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-414&amp;quot; /&amp;gt;&lt;br /&gt;
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The final scenario record should identify the initiating event, fuel and oxidant state, ignition mechanism, enclosure, pressure response and exposed targets. It should also state which uncertainties could change the mechanism, including possible transition to detonation. This keeps the selected protection tied to the physical event rather than to a generic explosion label. The record should also distinguish demonstrated performance from assumptions that still require test evidence or further analysis. Each assumption should remain traceable to its supporting document, test or explicitly justified judgement.&amp;lt;ref name=&amp;quot;Zalosh-3-402&amp;quot; /&amp;gt;&amp;lt;ref name=&amp;quot;Zalosh-3-412&amp;quot; /&amp;gt;&lt;br /&gt;
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== See also ==&lt;br /&gt;
&lt;br /&gt;
* [[Fireball]]&lt;br /&gt;
* [[Flammability limits]]&lt;br /&gt;
* [[Premixed flame]]&lt;br /&gt;
* [[TNT equivalence]]&lt;br /&gt;
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== Notes ==&lt;br /&gt;
&lt;br /&gt;
&amp;lt;ref name=&amp;quot;Zalosh-3-404&amp;quot;&amp;gt;Zalosh (2002), pp. 3-404–3-405.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&amp;lt;ref name=&amp;quot;Zalosh-3-415&amp;quot;&amp;gt;Zalosh (2002), pp. 3-415–3-416.&amp;lt;/ref&amp;gt;&lt;br /&gt;
&amp;lt;references /&amp;gt;&lt;br /&gt;
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== References ==&lt;br /&gt;
&lt;br /&gt;
* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno (Ed.), &amp;#039;&amp;#039;SFPE handbook of fire protection engineering&amp;#039;&amp;#039; (3rd ed.). National Fire Protection Association.&lt;br /&gt;
* U.S. Nuclear Regulatory Commission. (2005). &amp;#039;&amp;#039;Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program&amp;#039;&amp;#039; (NUREG-1805). Author.&lt;br /&gt;
* Van Rossum, E. (2027). &amp;#039;&amp;#039;Introduction to Fire Safety Engineering&amp;#039;&amp;#039;. Fire Safety Academy.&lt;br /&gt;
* Zalosh, R. (2002). Explosion protection. In P. J. DiNenno (Ed.), &amp;#039;&amp;#039;SFPE handbook of fire protection engineering&amp;#039;&amp;#039; (3rd ed.). National Fire Protection Association.&lt;br /&gt;
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[[Category:Explosions &amp;amp; Industrial Fires]]&lt;/div&gt;</summary>
		<author><name>Jan</name></author>
	</entry>
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