8/3/2019 2004 02 Flammable Gas in Enclosed Space

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How This Relates to Process Safety andHow This Relates to Process Safety and

What You Can Do to be Safe !What You Can Do to be Safe !

This event may seem to have little relationship to process safetyin chemical plants, but NUMEROUS building and vessel

explosions have occurred under similar conditions!!!

• Storing flammables of any kind in an enclosed area is

risky business. Small leaks can lead to flammablemixtures in a portion of, or an entire building. Then, onlyan ignition source is needed—and, ignition sources arevery easy to find!

• Store flammable liquids in containers and cabinetsspecially designed for such use. Be especially alert forsolvents used in maintenance activities.

• Store flammable gases in the open or well ventilatedareas so that small leaks can dissipate and NOTaccumulate. Particularly watch out for instrument

calibration gases and welding bottles.• Remember that some gases are heavier than air andsome are lighter. Provide the appropriate ventilation.

• Know and consider where and how explosive mixturesmight accumulate in piping systems or process vessels,such as in the head space of atmospheric tanks. Beprepared to recognize when flammables are present andreact quickly to prevent ignition.

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Messages for Manufacturing Personnel

February 2004

Here’s What Happened:

How Did This Happen?

• Acetylene is one of those

gases that has a very wide

flammability range. In fact,acetylene is flammable in

concentrations from 2.5% to

82% in air.

• It took only a very small

leak to eventually fill the cab

of this truck with the ¼ pound

of acetylene needed to reach a

flammable mixture.

• When the door was opened,

the flammable mixture

“found” an ignition source.

• In this case, the driver was

seriously injured, but luckily,

was not killed.

CENTER FOR 

CHEMICAL PROCESS SAFETY

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SS

Flammable Gas in Enclosed Space = BOOM !Flammable Gas in Enclosed Space = BOOM !

A pickup truck with a small

cylinder of acetylene stored

in the cab was parked for the

weekend. Unfortunately, the

cylinder had a VERY small

leak. Because all the

windows were closed, a

flammable atmosphere was

developed inside the truck’s

cab. When the owner returned on Monday and

opened the door---BOOM.

You can see the results.

Flammable materials in unventilated areas is an explosion waiting to happen! 

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