Aircraft Maintenance and Methyl Benzotriazole

A friend of mine sent me pictures of a 757 being deiced in upstate New York. The deice truck had an enclosed ‘bucket’ that housed the deice applier (in its early days, we referred to that as the ‘glass coffin’). It immediately brought back memories of me spraying a 727 in an open bucket at the end of a very tall boom, or worse deicing from a tall stand being pushed by a tug.
The fun part of the open bucket-on-a-boom was that after the radio controls got gummed up by glycol and water; my driver couldn’t hear my yelling STO-O-OP! as I was nearly decapitated by the trailing edges of the 727’s elevators. Oh, and by the way, the reason I didn’t lower the boom was because the radios weren’t the only controls that got gummed up. That, plus my driver’s interpreting the term ‘Ramp Speed’ as ‘Ramming Speed’. “Hello, Mrs. Carbone? Yeah, your husband lost his head at work.”
Those were the days we could see the hazards. At least we thought we did.
It turns out the sharp edges of an elevator weren’t the only danger for deicers; there was also the Methyl Benzotriazole – or MeBT – that was in the air. What is Methyl … I mean, MeBT? It’s a lubricant. Furthermore, it’s a carcinogen. And not just any carcinogen, MeBT is a quick acting cancer agent.
Where does a lubricant fit into deicing? The manufacturer of deicing fluids mixes it with the pure glycol or polypropylene glycol during manufacture. It is used to lubricate the hot deice pump’s internal gears while applying deice fluid on the aircraft. Without it the gears would eventually seize or become a maintenance burden.
Now, MeBT isn’t a standard carcinogen. You can rub it into your skin with little to no effect, unless you use it as a cologne (not recommended). One could probably drink it straight (or with a twist of lime) and be unaffected … except for some very unpleasant stomach distress. No, MeBT’s cancer causing super power is most dangerous when it is being inhaled; it goes right for the lungs and a quick route to the bloodstream. Just like one would experience breathing in a heaping helping of deice steam as it blows in their face.
But, one may argue, I said the deicer’s bucket is enclosed, cut off from the outside environment. And, so I did; and be thankful that person is now safe. But when do airliners deice? Just before departure/pushback, often at the gate (according to the airline and/or the airport because an airline’s deicing program is individually approved and all are not alike). The hapless victims are now the cargo handlers, the mechanics at or near the deice gate, pilots walking around a neighboring airliner, airport security, or any number of authorized airport personnel within breathing distance. According to which way the wind blows determines who gets the MeBT to the lungs.
So, let’s be aware of not only the dangers we see, but those dangers that we can’t see. One doesn’t need a scuba tank, but instead one should be aware of the conditions and what’s going on nearby.
Even if it’s at a gate next door.

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