Hold Your Breath!

We have learned to forget the lessons our parents hammered into us regarding common sense: "Don't run with scissors!" "Your face is going to freeze that way!" "Get that out of your nose!" My favorite was when Mom yelled, "Use your breathing protection and don't inhale the methylbenzotriazole!"

You know how it is, you're in the boom of the de-ice truck on a cold snowy night, splashing hot aircraft de-icing fluids (ADF) over the tail of a 767. Suddenly a gust of wind blows the steamy fog of glycol and water back in your face. You instinctively do what hundreds of mechanics have done and still do; you breathe normally and take in a heaping lungful of that sweet-smelling fog. You think to yourself, "hey, this could be worse, it could smell like skunk. So what's the harm?" But do you really know what you're breathing?

I can almost see Mom now, standing near the rear entry door in her parka, tapping her foot and shaking her fur-lined hood. I'll bet she knows what you're breathing. So does the manufacturer of the anti-corrosive that gets mixed with your ADF.

When you check the material safety data sheet (MSDS) for de-icing fluid you will see the normal need-to-know data about what is contained inside the ADF. This information spells out harmful effects and how to treat someone who is exposed to these elements. What you won't find are some items that get mixed with the glycol. In some of these ADF mixtures is a substance called methylbenzotriazole (MeBT), also called tolyltriazole.

According to the Society of Environmental Toxicology and Che-mistry, MeBT is "commonly used in a variety of industrial and commercial fluids to inhibit metal corrosion." Because MeBT does not add to or take away from the effectiveness of the glycol, it need not be mentioned in a MSDS. It is a patented chemical that the manufacturer reserves the right to keep proprietary. This is a common practice aimed at guaranteeing rights protection, and the manufacturer is legally allowed to omit this information from a MSDS.

The MeBT is used primarily as an anti-corrosive for the de-ice vehicle's internal systems, working as a lubricant to coat the gears against the harmful effects of water. MeBT is not a normal component of de-ice fluid, and the amount of MeBT found with the ADF during testing is too trivial to be harmful during normal handling (on the skin, for example), especially in the natural undiluted state of the ADF.

However, MeBT is a suspected carcinogen, a cancer-causing agent. The problem is when the heated ADF breaks down into a vapor during application; the MeBT and glycol become airborne in the steam and is taken directly into the lungs.

This begs the question, "Steve, with the amount of chemicals we work with, what difference will a little MeBT make?" This is where the common sense part of your upbringing should kick in. For example, many mechanics, myself included, have washed their hands with straight methyl-ethyl ketone (MEK), even though we know we shouldn't. People in our profession drill out screws without using eye protection and hang precariously over the edge of a grease-spattered aircraft work platform.

Sometimes we do these things because we feel the laws of physics don't apply to us, that in many ways we are invincible. But sacrifice your hearing because headsets are uncomfortable or take one Skydrol shower and your views on safety go from lip service to action. The truth is that you can fall 25 feet to the ground, the metal chip will fly from the drill bit to find your left eye, and harmful chemicals will play havoc on your organs.

One lesson to learn is that even if the MSDS doesn't alert one to chemical dangers, precaution should always be taken.

Like any job we perform in this business, we need the tools to do the job right, no matter how small the task. In this case, consider the information you learned to be the tools you need. The other tools are the breathing protection, rubber gloves, and goggles. Now that we have the tools, we need to remember to play safe, for our own benefit.

I suggest we take precautions to prevent breathing the ADF. And while we are at it, stop washing your hands with MEK, take a moment and clean that grease off the work platform, and wear your hearing protection. I've personally rushed enough people to the hospital because they had their Superman status revoked.

Well, I'm not going to lecture you anymore. We are all adults and should know what's wrong or right. But whatever you do, don't breathe in that methylbenzotriazole! My Mom is probably watching you!

Steve Carbone is an Aviation Safety Inspector with the FAA in Washington, D.C., where one of his areas of expertise is aircraft de-icing. He holds both A&P mechanic certificates and has spent 20 years in the industry.