In a column written for the April issue of Industrial Safety & Hygiene News (TRAINING STRATEGIES: In a tight spot), I called upon several experts in help explain the particular challenges the construction industry faces when it comes to confined spaces, and how those challenges can be addressed by EHS professionals.

One of those experts, Edward J. Willwerth, has been good enough to answer a question about the topic from one of our readers -- and his information may prove useful to many more. Willwerth, an NFPA-certified marine chemist, has taught confined space safety courses for the U.S. military, shipyards, petroleum terminals, chemical manufacturers and industrial facilities. He has conducted thousands of confined spacesurveys and entries in over thirty years of service to the marine, chemical, petroleum and general industries and has been an independent consultant since 1989 as president of Atlantic Environmental & Marine Services, Inc.

So when Trevor Sterling of Ergos USA/Canada emailed me a question about a specific confined space danger, I turned once again to Willwerth, who graciously lent his expertise to the topic once again.

”Hi Maureen;” wrote Sterling. “I enjoyed your article. I have a question though: does heat in a confined space come into play when assigning work? And if so how and what are you required to do?”

Willwerth’s response:

Heat stress is a very serious physical hazard concern in CS work, and evaluation of conditions and appropriate levels of fresh air ventilation are key to assisting in its control.

As you probably know, however, the evaluation and tracking of potential heat stress parameters can be done, but is complicated. Careful monitoring of the space and its workers with appropriate (and expensive) equipment is involved.

But heat and the presence of water will also have an affect on oxygen content as well. In a space with ample standing water, as the temperature gets to approximately 102ËšF/39ËšC, the vapor pressure of water will reduce the concentration of oxygen to a point where, through displacement, it will be less than the 19.5%. This level is used as minimum acceptable oxygen level for unassisted entry (in 29CFR1910.146 and, evidently, unless something changes, (in the proposed OSHA construction standard), or for nearly all work entry (in 29CFR1915).

Though this allows someone monitoring the space's conditions a good reason (I.e., poor oxygen levels) to stop work in the space, the real reason to stop work would be the space’s heat and humidity giving the likelihood of heat stroke.


There you go, Trevor, and thank you Mr. Willwerth.