How Much Fuel Can I Store at Home? What Are the Risks?

Here's a cautionary tale about the amount of energy packed into common liquid hydrocarbon fuels - and why you need to be immensely careful with them if you store even a small quantity of petrol - say five litres - in the home (say for the mower). 

At 11.28am, Saturday 12 August 2000, a massive explosion ripped through the Barents Sea in the Arctic. It measured 1.5 on the Richter scale. A Soviet 65-76 torpedo aboard the Russian Submarine, the Kursk, ‘malfunctioned’. The subsequent events ripped the front end off a 23,000-tonne steel vessel twice as long as a Boeing 747, built to withstand hundreds of metres of water pressure. It killed 118 Russian Seamen, some mercifully quickly; others neither mercifully nor quickly.

The disaster is described in Robert Moore’s nail-biting book, A Time to Die, which is a ripping good (albeit macabre) read.

A torpedo is a delivery system for a high-explosive warhead. It’s a massive machine capable of punching itself through the water at around 60km/h, with a range of about 80km. It requires a lot of fuel. In fact, there’s significantly more energy stored in the fuel than in the explosive warhead.

The explosive is designed to go ‘bang’ all at once, but the fuel is designed to burn continuously, for propulsion. Kerosene was the fuel. Oxygen (for combustion) was supplied using a concentrated form of hydrogen peroxide called ‘high-test peroxide’. It was necessary because the torpedo operates under water – an environment that doesn’t sustain combustion. It also delivers a great deal of oxygen, quickly.

It was the fuel that sunk the Kursk, not the explosives. Five hundred kilograms of kerosene came into contact with 1000kg of peroxide – an unimaginably catastrophic event. A seal in the torpedo probably failed – nobody knows – allowing the two chemicals to mix. The ensuing reaction is violent and spontaneous, and no known fire-fighting equipment can stop it once it kicks off. It simply erupts at breakneck speed until the chemicals are exhausted.

If you happen to be in an enclosed metal box with it when it happens, well, that’s bad news for you.

The explosion ripped through the torpedo room and engulfed the adjacent command centre. It disabled the Kursk, which impacted the 115-metre-deep seabed two-and-a-bit minutes later. Then all the remaining torpedoes in the nose, all the explosive and all the fuel, erupted. That second blast measured 3.5 on the Richter scale.

Kerosene has a similar amount of energy locked inside it as petrol, litre for litre. Half a tonne of the stuff is around 700 litres – call it 15 average car-sized fuel tanks full. It makes you think.

Most people have no idea about the massive amounts of energy locked up inside petrol, diesel, kero, etc. An 1800kg car cruising down the highway has 800kJ (kilojoules) of kinetic (motion) energy. That’s a lot. If it hits a massive tree, the destruction arising from the structure absorbing all that energy quickly will render the vehicle unrecognisable. The people inside will not survive. Yet there’s 800kJ of chemical ‘combustion’ energy locked inside just 25ml of petrol – that means every jerry can carries inside it roughly the same energy as 800 1.8-tonne cars all travelling at 110km/h.

Put it another way: every jerry can carries the explosive potential of 800 cars impacting something at 110km/h. Every full tank of petrol is equivalent to 2500 cars smashing into something simultaneously, at the freeway limit.

It’s scary – especially when people store fuel at home. Five litres of it is enough to make a sizeable bomb – 200 cars all ramming into the house at 110km/h. You could easily make a Molotov of yourself, however unwittingly, if you’re a goose about it.

There are, of course, regulations. Only nobody polices them, really. They vary from state to state. In NSW, five litres is the most you’re allowed to store inside a dwelling. I guess that’s allowed because inner-city terrace house dwellers need to store the fuel for the mower in the laundry, or something – otherwise, why the hell would a sane person keep any petrol inside the house?

Twenty-five litres (1000 cars hitting something at 110km/h…) is the maximum allowed in an attached garage … provided there’s a fire-rated wall between it and the house. Worryingly, you’re allowed to store up to 100 litres (4000 cars…) in a shed or outdoors – at least one metre away from other dwellings.

If you want to store more than 100 litres at home – obvious question: Why? – the Occupational Health and Safety Act kicks in. You’re required to conduct a formal risk assessment and implement hazard control measures … although it’s unlikely a Workcover inspector will ever check up on you.

Even more stupidly, you’re allowed to store 250 litres outdoors or in a structure three metres away from the boundary or other dwellings. Above that, you need to post a ‘Hazchem’ sign on the street frontage and a yellow ‘Flammable Liquid’ diamond sign (like the one on fuel tankers). The neighbours will probably arc up about that, and then there will be a subsequent stern chat with the local council...

The regulations are, frankly, ridiculous. The obvious answer to the question about how much fuel you should store at home is: As little as possible – because you really don’t want to orchestrate your own on-dry-land version of the Kursk disaster any time soon.