LPG Leak, What Would You Do?

Electricity and Magnetism Level 2

James arrived home after a party and realized that he had forgot to turn off the knob of the gas line. There is a strong smell of liquefied petroleum gas in his apartment.

What should he do to avoid any accidents?

Turn off the knob of the gas line.
Open all the windows.
Turn on the exhaust fan.
Turn off all the electrical appliances.

1 only 1 and 2 only 1, 2 and 3 only 1, 2 and 4 only 1, 2, 3 and 4

2 solutions

Rohit Gupta
Feb 20, 2017

This problem uses the concept of self-inductance. Whenever the current flowing in a coil change with time, the flux linked with it also changes, therefore, according to Lenz's law , an emf is generated in the coil which opposes this change in the current. The quicker the current changes, the greater the emf is generated. This is the reason why we often see a spark when we either switch on or even switch off an electrical device.

Therefore, we will not want to switch on or off any electrical device in case of an LPG leak, because doing so may cause a spark which can be hazardous.

Moderator note:

This is an excellent, practical demonstration of induction. And it may save a life. Many people would instinctively turn off all electronics, thinking the live current is the only consideration when it comes to sparking the gas.

I would especially turn off the electricity to the whole house. If your refrigerator compressor switches on or you have an active cycling device such as a charger to a phone near enough to the leak or concentration of gas....boom. That's why kill switches are located on the outside of buildings and far away from electrical hazards in confined spaces.

Charles Nightingale - 3 years, 11 months ago

It depends where the power switch is located. If you disconect the electricity to the house and thus turn off the appliances - there will be no spark at the area of the gas leak and it will be safer.

Ilan Amity - 4 years, 3 months ago

I don't think there is any reason for switching on or off any electrical appliances after cutting the electricity. Unless you want to switch off the electrical appliances anyhow. The question focuses on that if an electrical appliance is running at a place where the LPG is leaked would you want to turn it off? The answer is no as it is not producing any spark and switching it off may result in a spark at the switch/in the electrical appliance.

Rohit Gupta - 4 years, 3 months ago

I didn't understand how LPG can lead to a spark.

Rajdeep Bharati - 3 years, 12 months ago

@Rajdeep Bharati – Not the LPG, but switching on and off an electrical appliance can cause a spark, and then LPG will start burning.

Rohit Gupta - 3 years, 12 months ago

@Rohit Gupta – ok, understood

Rajdeep Bharati - 3 years, 12 months ago

As to the fan, it's not just turning it on that's dangerous; having a fan running is extremely dangerous, unless it's rated "explosion-proof". Electric motors have brushes that make and break contact hundreds of times per second. Any chemist who has worked in a lab more than a few months knows that electric motors are one of the most insidious spark sources in any facility, and if there is a flammable/explosive atmosphere, they must be turned off by unplugging immediately. If the plug is in the explosive atmosphere (spill outside the fume hood, for example), you should cut the power at the nearest breaker outside the explosive vapors.

Eric Lucas - 4 years ago

This is an excellent point.

Rohit Gupta - 4 years ago

Great answer. But what effect will exhaust fan have on this, can you explain?

Kapu Rkk - 4 years, 3 months ago

Yes, as I said when you switch on the exhaust there may be a slight spark in the switch which may cause a fire.

Rohit Gupta - 4 years, 3 months ago

Should you open all the windows? That would have to be done from inside the house, and you could be overcome by the gas while attempting it.

Robert Beggs - 3 years, 11 months ago

That's brilliant!

Muhammad Rasel Parvej - 3 years, 11 months ago

I chose turning off the knob only. Introducing air (O2) into the room by opening a window makes the recipe for an explosion imminent. Obviously, using any electric device is the absolute wrong thing to do based on the inductance principle. The answer to this question (1+2) is flawed.

General Alist - 3 years, 9 months ago

i would do the opposite, and unlock the window only (while technically leaving it mostly closed), the stove might have auto ignition in which case turnung it off would also trigger the sparks. thats why my second step would be running outside and turning off the main electricity and gas. and then i can open the windows from the outside to finally get rid of the gas

Ken Sammed - 2 years, 10 months ago

Apoorva Gupta
May 22, 2017

Only 1 & 2 is is correct because electric aplienses are dangerous to on off when gas on.

LPG Leak, What Would You Do?

2 solutions

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