Many of us have heard the expression, "Canary in a coal mine." It refers to a time when miners would carry caged birds with them as they entered mine tunnels. If the miners encountered dangerous gases such as carbon monoxide, the gases would kill the canary before killing the miners, allowing them to escape safely. It turns out the military has a similar warning process in the event of a chemical attack, but instead of using canaries, they could use... you.


That's right, Field Manual 3-11.4 "Unmasking Procedures Without the M256-Series Chemical Detector Kit" states: "If an M256-series kit is not available ... the senior person should select one or two individuals. They take a deep breath, hold it, and break the seal for 15 seconds, keeping their eyes wide open." The procedure is called, "Selective Unmasking," which is surprisingly calming for what is actually happening.

Basically, if the $H%T hits the fan, you can be ordered by your command to take off your mask and take one for the team ... just like a human canary. (Worth noting: the U.S. Air Force determined that this process is not within their acceptable range of risk. Not shocking.) Now, before you decide to run for your DD-214, know that we can't find one recorded event of Selective Unmasking ever happening with deadly consequences. There have been false alarms, such as during the chemical threats from Saddam's forces during the 2003 invasion, but everyone walked away safely, except for a few angry individuals.

While seemingly insane, Selective Unmasking is based on the same logic used to test poisonous plants in the wild, I.e., expose yourself to a limited dose for a short period of time and wait to see what happens. According to the Chemical, Biological, Radiological, and Nuclear Defense handout from the Marine Corps The Basic School, senior leaders will use the following steps when ordering a Selective Unmasking:

  • Designate two-three Marines
  • Brief them on the procedures to be followed
  • Have them sit in a shaded area out of direct sunlight
  • Ensure they are unarmed ------(Wonder why?)
  • The selected Marines will:
    • Take a deep breath.
    • Keep their eyes open.
    • Break the seal of their masks for fifteen seconds.
    • Then reseal and clear their masks.
    • Wait for ten minutes.

Now, if you're a gung-ho hard charger you can always volunteer to be a human canary. But, if you're facing some real chemical threats such as Anthrax, Sarin or Mustard, you might want to think twice. Certain agents can cause blistering, choking or even seizures. To avoid the chance of being chosen, you will have to play some unit politics.

Here's our advice on how to avoid Selective Unmasking:

1. Rank has its privileges.

Officers, NCOs and unit leaders are mostly vital to the mission and will most likely not get picked. That leaves junior enlisted or new arrivals to the unit. So take promotion seriously before you enter a chemical battlefield.

2. Don't be a dirtbag (or the new guy).

Your CO and NCO's know how much value you are bringing to the unit on a daily basis. Dirtbags can cause their chain of command endless hours of paperwork and new arrivals haven't even had a chance to prove themselves. If you aren't fitting into the team good luck and on that note.

3. Luck

In a chemical attack, get your MOPP gear on and keep your head down. That being said, fighting during a real chemical attack is going to suck so start racking up karma points now.

Selective Unmasking is by far a last resort in one of the worst situations on earth. All of this can be avoided with proper planning and pre combat checks so bottom line....bring your test kits!