How long for petrol fumes clear?

[Cris B]

In preparation for starting my project I removed all the fuel lines and tank from the shell today. All the fuel has been decanted in petrol cans - these are proper petrol sealed containers and will be well away from my work area.

I managed to miss the funnel once or twice and there was some leakage from the hoses as they came out. I've soaked it up and thrown out all the paper towel and lines, so in theory the only source for vapour is now what's soaked into the concrete floor. How long should I leave this to evaporate before starting welding?

 

[RedOrZed]

Wash it down with water. Put down some sand or cat litter on the floor, should soak it all up quite quickly.

If you've remove the tank to a safe distance there shouldn't be a problem. I don't think I'd worry about petrol vapour unless it was in large amounts.

However, this is the internet and you don't know me from a hole in your head - take care!

 

[voipio]

Is there still a strong smell of petrol, especially close to the ground? If the answer is yes, hold off on the welding! Since petrol vapour is quite a bit denser than air, it will tend to sink fairly quickly and accumulate in hollows. One of the worst places for accumulation of fuel vapours is an inspection pit, but hollows in a body shell (e.g. a boot) can also accumulate vapour.

Whenever mopping up solvents such as petrol, with paper towel, it's best not to put the towel straight in a bin, because the vapours will sink to the bottom of the bin. Instead, leave the towel in a well ventilated place for the solvent to evaporate first.

Keep the area well ventilated. It doesn't have to be a gale, just a gentle draught. This will minimise the chances of flammable concentrations of fuel being reached.

As a test, I've poured about a third of a cupful of petrol onto our patio, left it a couple of minutes, and tried without success to ignite the patch. There was a gentle breeze which probably helped.

The inflammability limits for petrol-air mixtures are quite narrow - about 1.5-7.5% fuel by volume in air. The fireballs produced by throwing a cigarette butt onto a trail of petrol, as seen in Hollywood movies, are actually nigh on impossible to achieve.

As a previous poster said, take care.

 

[gavuk]

A cigarette will never light petrol, doesn't burn hot enough ,sparks from welding or grinding are a different matter and have the potential to ignite petrol vapour..........a couple of hours,with air movement , should be more than enough to clear flammable vapour but it would depend on the quantity,and as mentioned ,drains, pits and anything lower where vapour might collect should be treated with caution still ....

 

[Cris B]

Thanks folks, some useful tips!

 

[Iain Westland]

you can def start welding now

 

[gavuk]

you can def start welding now

and thats why you were missed Ian

 

[Superbad]

I've just welded a used petrol tank. It must have been no more than a month since I emptied the tank