gas / air mix % needed for explosive atmosphere?

[Soundguy]

A question came up in another sub about how much concentration of gas ( lp , etc ) is neede din the local atmosphere before it is dangerous and explosive.

I know I've seen discussions about this around here and believe we have a few 'gas' people around here.

Soundguy

 

[txdon]

Soundguy, the most common gases encountered in a fire and explosion are natural gas and commercial propane.

Natural gas is lighter than air and has a vapor density of 0.59 to 0.72. The lower explosive limit (LEL) is 3.9% to 4.5% and the upper explosive limit (UEL) is 14.5% to 15%. Its ignition temperature is 900 degrees to 1170 degrees.

Commercial propane is heavier than air and has a LEL of 2.15% to 2% and an UEL of 9.6%. Ignition temp is 920 to 1120 degrees.

Source- NFPA guide 921

 

[Bob_Skurka]

Don, I believe propane is the far more dangerous gas in terms of accidental explosions.

Because it is heavier than air, a leak can cause a pool of propane to fill an area. You don't see a lot of propane used on sail boats anymore because a leak could fill the bildge and the bildge pump could trigger an explosion that would sink the boat. (on those that do have propane, the tanks are held outside the cabin and vented to drain the gas overboard) Similar thing could easily happen in any confined area with propane if it has a place where it can settle. While propane for an outdoor BBQ grill is safe simply because a light wind will disperse it.

 

[Soundguy]

Cool guys.. that's what I needed.

Looks like in open spaces.. gas in general is pretty safe. Looking at lowest number.. 2%.. that's hard to get in an area with any wind at all.

Soundguy