Talk:Explosive limit

A google suggests this could be made into a valid page. I've listed it on cleanup. EddEdmondson 13:56, 16 Jun 2004 (UTC)

Definition of concentration

Most commonly gasses are specified as volume % concentration in volume.--Thydzik 14:31, 7 November 2005 (UTC)

The the explosion limit table applies, to standard temperature and pressure in air.

Influence of Pressure

Explosive limits also change with altitude and pressure. International Critical Tables, "Explosions and Gaseous explosives," page 181 shows H2-O2 upper explosive limit drops to 50% at 9 kPa. Finucane1 08:15, 5 December 2006 (UTC)

Flammability limits and Explosive limits

I have seen sources that distinguish the two, but mostly just one is given and called by either name. Does anyone know more about this difference? How should it be reflected in Wikipedia? (The articles should probably be merged nonetheless.) The way, the truth, and the light 09:51, 15 June 2007 (UTC)

The temperature at which a flame can be supported relates to flammability limits; the temperature at which an explosion can occure related to explosive limits. The two temperature ranges can be slightly different. Any merged article should end up identifying and distinguishing the two. Pzavon 01:50, 18 June 2007 (UTC)

Both measures, according to our articles and sources I've seen them in, are concentrations, not temperatures; so I don't follow you. It's true that concentration can affect the temperature reached during combustion, though. The way, the truth, and the light 09:59, 18 June 2007 (UTC)

Sorry, I "mis-spoke." Substitute "concentration in air" for "temperature" in my note above. It was late and I was tired. Pzavon 02:02, 19 June 2007 (UTC)

Flammability limits and explosive limits are not the same and, therefore, the topics should not be merged.

The above unsigned comment was made on 1 August 2007 by 38.112.12.110

They are very similar and are often confused. Therefore an agrument can be made that an article combining both would be better than two separate articles as the overlap/duplication can be eliminated and the differences and similarities can be clearly discussed. Pzavon 01:39, 2 August 2007 (UTC)

Personally, i feel that the two topics should not be combined. I suggest "flammability" and "explosive" limit should not be confused, however similiar the two might be related, as both are different in context. "Flammability limits", as stated in the article, states that it is the proportion of combustible gases in a mixture, between which limits this mixture is flammable. However, "explosive limits" is a much higher propotion as it states that it is the limiting concentration (in air) that is needed for the gas to ignite and explode. However similiar in text, "explosive limits" is related to the flammation and explosion of the

combustible gas/gases, instead of just the limit to the propotion of gas in air to just be ingnited, as in "flammability limits".

I suggest the that two topics be linked for the time being, until a audit has been made to the to topics, to further differentiate both topics. Zep fire 14:38, 14 August 2007 (UTC)

Whether or not they should be confused, the fact is that they are confused by many. A single article addressing both would most effectively be able to discuss differences and similarities and prevent that confusion. Pzavon 01:31, 15 August 2007 (UTC)

Pzavon, you do have a valid point there. Perhaps the two pages should be combined as one temporarily, for the convenience of discussing both topics simultaneously. But, if there are more information to further differentiate between the two. I belief they should be separated at a later point in time, as both topics are different scientifically when u talk about the definition of the two terms. As such I hope to be exact in providing information and also clearly defining the lines. Zep fire 09:47, 27 August 2007 (UTC)

The "flash point" of a vapor is the minimum temperature at which its vapor pressure is sufficient to form a flammable vapor-air mixture at 1 atm. pressure. Note that flash point is a temperature and not a vapor concentration. Whether or not the vapor explodes upon ignition is largely a function of the setting (e.g. whether or not the ignited vapor is confined). The Lower Flammability Limit (or lower explosive limit in a confined space) is a concentration of hydrocarbon and air mixture high enough to ignite in the presence of an ignition source (usually around 3% hydrocarbon). The flash point of a hydrocarbon mixture can be used to calculate the Lower Flamability Limit through use of Antoine vapor coefficients and partial pressure of the constituents. EPA-NEIC October 11, 2007 —Preceding unsigned comment added by 134.67.6.15 (talk) 20:33, 11 October 2007 (UTC)

The flammable limits and explosive limits are the same thing. I am on the ASTM committee that develops the standards for these things and they are the same. About 20 years ago explosive limits were more popular in usage than flammability limits, but now flammable limits are used more commonly. The flammable limit is actually a better designation since it implies that a fire can occur.--Engineerche (talk) 00:33, 16 March 2008 (UTC)

Flammable limits and explosive limits are typically used synonymously and express the point at which a gas-air mixture will ignite and combust. The difference between something burning or exploding is down to whether the mixture generates an increase in pressure i.e. an explosion. This can happen due to containment or the mixture detonating. A detonation happens at different concentration limits (Perry’s Chemical Engineers Handbook, 7th Ed) to those typically quoted and is related to the energy release in the combustion sustaining a supersonic pressure wave. At flammable limits the energy release is insufficient to create the pressure wave needed to ignite the flammable mixture. Hence flammable limit is more descriptive for the typically used values and perhaps the explosive limit should relate to the detonability figures (although generally it doesn’t). As flammable limit and explosive limit are often used interchangeably, I suggest putting them on one page to keep the information all together. —Preceding unsigned comment added by 20.133.8.132 (talk) 09:39, 28 August 2008 (UTC)

I favor combining the discussion of flammability limits and explosive limits (athat they are synonymous is not obvious to those new to the subject. I would go further and clarify the distinction between the flammability limit and the detonation limit in the same article, and include both in a single table.

Properties of Hydrogen Property Hydrogen Methane Propane Gasoline Lower Flammability Limit (%) 4 5.3 1.7 1.3 Lower Detonation Limit (%) 18.3 6.3 3.1 1.1 Upper Detonation Limit (%) 59 13.5 9.2 3.3 Upper Flammability Limit (%) 75 17 10.9 6.0 Auto Ignition Temperature 585 C 537 C 450 C 215 C Minimum Ignition Energy 0.017 mL 0.274 mJ 0.240 mJ 0.240 mJ

from “Companion Guide to Hydrogen: The Matter of Safety,” Hydrogen 2000 and Plug Power Inc.

According to the article, explosion implies confinement (as defined in some NFPA standard or other, undoubtedly appropriate to the subject). Other sources (and the previous writer) treat detonation as an explosion even if it is unconfined. Perhaps this point should be clarified. —Preceding unsigned comment added by 148.184.174.61 (talk) 20:54, 15 September 2008 (UTC)

Estimating Gasoline Concentration & Safety

It seems that gasoline can be detected by smell at about 10 ppm. However, I don't know how to convert that to % by volume of air. It may be too specific to add a bit about this, but it might give readers intuition about the lower limit for gasoline, which many people have some experience. neffk (talk) 04:16, 11 March 2008 (UTC)

1 percent is 1 part per hundred

10 ppm is 0.0010 percent (one one-thousandth of a percent)

I don't think puting such a factoid in the article is useful. It is merely one more example of using very big or very little numbers to awe those who do not feel comfortable with them. Pzavon (talk) 00:31, 12 March 2008 (UTC)

oxygen concentration

What happens to the LEL/UEL of a compound as the Oxygen concentration increases? Do the LEL and UEL lower, stay the same or increases at higher concentrations of Oxygen? —Preceding unsigned comment added by 209.232.100.207 (talk) 21:19, 24 March 2008 (UTC)

Greater Oxygen concentration will lower the LEL and increase the UEL. Pzavon (talk) 02:48, 25 March 2008 (UTC)

what does an LEL meter detect? oxygen levels or specific contaminant concentrations? how does it handle mixtures?

Most LEL meters use a heated catalytic bead [[1]] as one leg of a wheatstone bridge. The sensor contains a second, non-catalytic leg of the bridge to act as a reference.

When combustible molecules hit the bead they are combusted, raising the temperature further, and the heat changes the resistance of that leg, changing the current passing through, which the instrument interprets as flammability.

Obviously some parameters that can affect this process include the amount of oxygen, the temperature, the species the instrument is calibrated for, and the species being measured. It is common, for example, to calibrate a combustible gas indicator for pentane using a pentane standard, typically at 50% of the LEL. When measuring methane however, this makes the meter read high.

Most CGI instruments used for confined space entry purposes are calibrated using methane, or a methane-equivalent concentration of pentane.151.204.179.162 (talk) 19:18, 28 August 2008 (UTC)

If someone can plainly word the difference between ignition and explosion, I would be impressed. Perhaps an example of a compound that has a different LEL than LFL, so we can see the difference.

Do you mean the difference between fire and explosion? As I understand it, the difference comes down to the speed of flame propagation, the proper comparative term is deflagration[[2]] versus detonation[[3]], deflagration is subsonic to sonic, detonation is supersonic.151.204.179.162 (talk) 19:18, 28 August 2008 (UTC)

I'm trying to get a handle on a vapor composed of multiple components...each with their own Explosive Range... when does the sum of the contributions push over the GROUP UEL? ie.. too rich to burn? along the same line of thinking... when does a group of compounds - each below their respective LELs - combine to make an explosive mixture? Hence the question about the LEL meters industry uses. What's it sniffing? False security?

Thanks. Lamijada (talk) 16:36, 14 May 2008 (UTC)