Monday, March 12, 2012

Who here recognises the smell of natural gas?

Well- in truth hardly anyone, but you do recognize the Mercaptain that is use to make it smell like it does.

Because Natural gas is usually colorless and odorless (unless it's really rich with other hydrocarbons that kind of make it smell like paint thinner), and undetectable without specific instruments.

That changed March 18, 1937 in a Texas school in New London when undetected gas exploded and killed 293 teachers and students.
It's now a Federal law that all natural gas be odorized with that distinctive skunk piss.

Here are some facts about natural gas that you may or may not know-
Remember the fire triangle you learned about in school? Add another leg to it and call it a pyramid.
Now you have oxygen, fuel, ignition and then gas concentration.
Natural gas will only burn (or explode) when the concentration is from 4.5- 14.5% gas-in-air. If it's above or below that, you can light matches all day long with nothing happening.

Of course if there is any air movement at all, you don't know *where* that pocket of flammability is which is why the authorities use excessive caution with a gas break.

An electric spark is right in that flammability sweet-spot. That is why, if you smell gas- you don't turn anything on or off.

AND Carbon Monoxide...that's even more flammable.

1 comment:

  1. I was working in a rail car repair facility, when the cleaning crew removed the dome on a mercaptan tank car. The reaction was to clear the office, look for the contractor (us) that broke the gas line and finally: sheepish grins with apologies.

    The incident reminded me of listening to a worker that had the job of placing the ethyl mercaptan in the "pots" on the transmission pipe. He couldn't eat in restaurants because the tiny amounts on his clothes would clear the room as soon as he entered.