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November 18

Open-air dust explosions

Dust explosion#Conditions required says There are five necessary conditions for a dust explosion. It even has a pointless diagram that arranges the five conditions in a pentagon with "dust explosion" in the middle. Condition 5 is confinement. But further down the page, Dust_explosion#Mechanism has a series of photographs demonstrating a dust explosion in open air. And thermobaric weapons, although more effective at killing people in confined spaces, seem to explode just fine in the open. So is condition 5, as a "necessary condition", plain wrong, perhaps an exaggeration of the fact that confinement makes a dust explosion more likely?

Supplementary question: I hear residents of Lahore and Delhi are wondering if their very sooty smog might one day explode. Is this at all plausible? Card Zero (talk) 00:09, 18 November 2024 (UTC)[reply]

Pointless? It is a five-pointed diagram. --Lambiam 06:53, 18 November 2024 (UTC)[reply]

In general, not only for dust, for detonation to occur, a mix of fuel and oxygen within the explosive limits has to be present in a compact largish volume. Upon detonation, the pressure in this volume will rapidly increase tremendously within (typically) microseconds. If the volume is not confined by an enclosure, the gases resulting from the combustion will expand supersonically with a shock wave that may or may not cause damage, depending on the power released and the environment. If the volume is confined by an enclosure, the enclosure may be able to withstand the pressure and contain the gases – possibly with controlled release through safety valves. (See e.g. Pyréolophore.) Otherwise, if the enclosure is broached, the gases will also expand explosively.

The OSHA fact sheet that is the source of our five-pointed list of conditions is actually about another scenario. It considers the case in which ignition merely leads to deflagration, which is much more likely to occur – the mix only has to be within inflammability limits. The combustion is much slower and does by itself not cause a shock wave. However, although the pressure rises less rapidly, the rise is still dramatic, especially if the volume is contained by an enclosure. If the enclosure cannot withstand the pressure, the gases will also expand explosively, as before.

So I think a fuel–oxygen explosion can occur in open air, but for this to be an explosion in the strict sense of causing shock waves, the right conditions will only very rarely be fulfilled accidentally. (In thermobaric weapons, they are fulfilled by design.) --Lambiam 09:05, 18 November 2024 (UTC)[reply]

But in the conditions there is no requirement of an accidental event?! 176.3.66.65 (talk) 15:10, 22 November 2024 (UTC)[reply]

The OSHA fact sheet does not deal with ways to mitigate the risk of intentional explosions, such as may be caused by weapons. You are free to see this as an omission; I doubt though they will agree. --Lambiam 12:00, 23 November 2024 (UTC)[reply]

Delayed onset muscle soreness

How long does it last and how to recover from it? CometVolcano (talk) 16:53, 18 November 2024 (UTC)[reply]

According to the article: "It peaks from 24 to 72 hours, then subsides and disappears up to seven days after exercise." --Amble (talk) 17:11, 18 November 2024 (UTC)[reply]

From the top of this page: We don't answer (and may remove) questions that require medical diagnosis... AndrewWTaylor (talk) 14:15, 19 November 2024 (UTC)[reply]

It is said that the soreness is helped by consuming protein. Abductive (reasoning) 10:27, 20 November 2024 (UTC)[reply]