Are home products flammable?

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

Image result for mortein control bomb

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.


Engine Coolants #1: Ethylene Glycol

That green stuff that you put in your radiator is ethylene glycol. The idea behind it is that it doesn’t boil or freeze easily. That is, it freezes significantly below zero degrees and boils at a substantially higher temperature than 100 degrees.

Also, the coolant contains antioxidants whose job is to stop your radiator and engine block corroding.

They are much more important in modern engines than they used to be, as modern engines are made from alloy and are therefore more prone to chemical attack. In older engines made of cast iron (old Holden engines) you could pretty much run tapwater in them and it wouldn’t make a whole lot of difference.

But modern engines need to be protected against corrosion, and so modern coolants with antioxidants are required.

But there’s something you have to watch out for. Coolants come with different concentrations of ethylene glycol – from about 5 or 10% up to 100%. It’s easy to think that more is better and just go for the 100% (usually called a concentrate) but there’s a problem with this.

The problem is that ethylene glycol has a lower heat capacity than water. So whereas it takes 1 calorie to heat 1 gram of water by 1 degree, it only takes 0.6 calorie to heat the EG by the same amount. And this is a problem when it is being used as a coolant of course, as it means that it gets hotter quicker, which is not what you want.

So go for a happy medium and run about 30% coolant – it’s do a better job of keeping your engine cool and will save you money.

Hardware Chemicals #1: Hydrochloric Acid

Hydrochloric acid is an extremely useful and versatile chemical that has many uses around the home.

Its usefulness comes from the fact that it is a very strong mineral acid that is nonetheless generally safe to have around. This is because its bark is worse than its bite. In its concentrated form you’ll see white fumes coming off it, and if you catch a whiff of it it’ll hit you in the nose like a sledgehammer. This property alone is a strong deterrent for children and pets.But these fumes are only an irritant – they are not toxic.

If you get it on your skin it’ll sting, but it won’t burn (like sulfuric acid). And if you got it in your eyes, they’d probably survive, although it’d sting like hell. But you should be wearing safety glasses and gloves when handling it anyway.

And it’s cheap. A 20L drum from the hardware store will only set you back about $45. And because it’s concentrated, it’ll last you a long time.

So what can you do with it?

For a start, it is an excellent weed and grass killer. Make it up at about 10% (500mL in a 5L garden sprayer), add a few handfuls of salt, make the whole lot up to the 5L mark and away you go. Spray it on weeds and grass that you want to kill and you’ll start to see results within 24hr. And it doesn’t matter if some gets on the soil – there are plenty of things in the soil that will neutralize it.

And if you find something that will survive this brew (unlikely) then just increase the concentration.

It’s also an excellent chemical for rejuvenating driveways. Cement is essentially an alkaline composite. As it’s exposed to the sun and air it develops a coating of cement dust, largely composed of limestone (calcium carbonate). A 10% solution of hydrochloric acid will strip off this layer and restore it to pristine condition. A clean with a high pressure water cleaner afterwards will remove any water marks and give it a uniform look.

Have you had tiles put down and the tilers have smeared grout over the tiles? No problem – a 5% solution of hydrochloric acid will get it off easily.

What are Acids?

I think my first experience of acids was an episode of batman, where the penguin demonstrated the potency of the acid that he was about to dunk Batman in by inserting his umbrella in it. When he pulled it out, the part that had been inserted had completely dissolved.

And this is the view of acids that most people have – potent, nasty chemicals that dissolve everything in their path.

Well, although there are acids that can dissolve all sorts of things, there is no acid that will do to the penguin’s umbrella what happened on the show.

Essentially we can place acids into two categories – mineral acids and organic acids. Mineral acids attack metals mostly, whereas organic acids attack organic material.

Also, acids may be categorised according to their strength, with the vast majority of acids being weak acids, and our bodies are full of them – amino acids, fatty acids and so on.

There actually aren’t many strong acids, and only one of them (hydrochloric acid) is available to the general public in a concentrated form. Other strong acids are sulfuric, nitric, perchloric, and hydrofluoric. That’s pretty much it, although there are several mixtures that are used to provide extra potency. Aqua Regia is a mix of 1 part nitric to 4 parts hydrochloric. Piranha solution is a mix of hydrogen peroxide and sulfuric acid, and chromic acid is a mix of sulfuric acid and potassium or sodium dichromate.

Tomorrow we’ll look at hydrochloric acid and see what it can be used for around the home.