Whether the result of perspiration or precipitation, it’s not at all unusual for the FR clothing worn by workers in the field to get damp. How does that moisture impact the level of protection you get from the garment? As it turns out, there is more than one answer to that question.
According to Tyndale’s Vice President of Technical, Scott Margolin, when it comes to FR protection, some moisture has no negative effect. “If anything,” adds Margolin, “damp clothing is even less likely to ignite.”
But that doesn’t mean that moisture poses no threat at all.
According to Margolin, it depends largely upon how damp the fabric is, and how much incident energy is available. “In general, a little dampness is a good thing. It reduces skin temperature and increases the mass of the fabric – both of which can actually give the wearer added protection.”
“Where you begin to see a possible risk increase is when a garment is soaked,” Margolin continues. “If there is an arc flash or flash fire that raises the temperature sufficiently to turn that moisture into steam, the wearer could be burned by that steam.” This is highly unlikely to occur in flash fire, but is possible in arc flash. Water is a far more efficient heat transmitter than air, and breathable AR/FR clothing is not engineered to protect against steam burns. So, a significant energy release could potentially lead to a steam burn for a worker wearing a wet garment.
Hugh Hoagland, another renowned expert on arc flash safety agrees; his research indicates that heat conducts to the body better with enough liquid present in the garment.1 Hoagland and Margolin both point out that a wet AR garment is much, much safer than non FR. It will not ignite and continue to burn, and therefore dramatically reduces burn injury.
So, experts agree that a wet FR garment still offers full flame resistance, and they also agree that there’s an increased potential for burns if the moisture flashes to steam – but this is extremely rare outside of the lab. It’s also worth noting that soaking wet clothing is more likely to cling to the wearer’s skin, eliminating the pocket of air that offers added insulation between a dry shirt and the wearer – creating another potential risk factor.
So what can you do to protect yourself? The best practice is to bring at least one extra FR shirt to the worksite and change shirts if your original garment becomes soaked with sweat or gets wet in the rain. Not only will you be eliminating unnecessary risk, the dry shirt is likely to keep you considerably more comfortable on the job.