From time to time I get asked whether any home products that we buy are a fire risk, particularly products with a flammable diamond like one of these:
What do these mean?
The flammable liquid label will be on many solvents such as metho, acetone, xylene or turps. The flammable gas logo will be on many aerosols, as they mostly use hydrocarbons such as butane or propane.
Flammability is determined by a test where they heat the liquid and expose the vapour above it to a flame. If the vapour flashes (ignites) below 61°C it is termed as flammable, and if it flashes above 61°C it is non-flammable. This means that it doesn’t need a diamond, and there are no special transport procedures involved.
If it burns at a temperature above 61°C it is termed “combustible” – like diesel. That’s why when you see a truck go past with “Combustible Liquid” written on the panel at the rear of the truck.
Now if these liquids are flammable then, yes, if you light them they will burn. So if you spill 20 litres of paint thinners on the floor, and then while you are thinking about how to wipe it up you light a smoke and toss the still-burning match onto the xylene you will have a problem. But that is about the only circumstance where you will have a problem.
But as far as the flammable gases go, there are unfortunately cases where explosions have occurred when people didn’t read the instructions. These have all been caused by foggers, such as this
What happens is this – people in a house or restaurant realise that they have a cockroach problem. So they look on the back of the can and realise that they will only need three or four cans for the entire establishment . But then they think ” if three cans will work then 30 cans will work better.” And here’s where the problem occurs.
You see for a flammable gas there is something called a lower explosive limit (LEL), which refers to the concentration of gas required to initiate an explosion. Used according to the instructions you would never reach the LEL, and there would be no problem. But if you ignore the warnings on the back of the can and use 10 times the number of tins required, then you can reach the LEL, and this is exactly what happened in a restaurant in Melbourne a few years ago.
But ordinary aerosols use a flammable gas in conjunction with a water based emulsion. This means that they won’t burn. But I can remember many years ago, , before the advent of water based formulas, a can of Mortein made an excellent flamethrower. You simply spray the contents of the can over a burning match and voila. But these products are long gone.