Nancy Pearce

Training Demonstration of Hazardous Atmospheres in Confined Spaces

Blog Post created by Nancy Pearce Employee on Oct 19, 2012

How do you demonstrate hazardous atmospheres to trainees?  A training video can only go so far to demonstrate this principle.   I once read an article that contained a “recipe” for setting up an excellent training prop that I have now used in training for many years.  It provides a very visual example of how an apparently benign looking enclosure such as a water tank or valve vault can actually be deadly.

Take a large office water cooler size empty water bottle.  How bad could a water bottle be after all?   Add a handful of leaves, tiny bit of dirt or some mulch, along with a couple of iron nails or springs or rebar.  Add a bit of water to wet everything and then cap the bottle.  Let it sit for several months, preferably in a warm location.   Looks fairly innocuous right?   Looks like a typical meter pit or vault.   Other than a tiny bit of decaying material in the bottom of the tank, the container looks safe but it may not be.  

Use a calibrated four gas meter to test this bottle after a few months.  You will likely find that the atmosphere is oxygen deficient and the LEL meter will indicate that there is a potentially explosive environment, most likely due to the methane formation.  You can recap this bottle and continue using it for future demonstrations. You may need to “recharge” the bottle periodically with more materials and water and cap it for a couple months between trainings.  

Many confined spaces contain all the same ingredients shown in the demonstration-metal ladders and equipment, dirt or debris and water.  I have found this demonstration to be an effective means to show training classes why they need to monitor all confined spaces, even if they did not previously contain chemicals. 

Do you have demonstrations or training ideas that you would be willing to share?  NFPA is working on development of a Best Practices Guide to Confined Spaces.   If you have any training ideas or other information that you would like to see included in the new document please let us know!    

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