The regulations for some countries we fly to require we spray the cabin with an insecticide before we can land there. I was operating a flight to Cuba the other day, which is one of these countries.
I’ve done this procedure countless times. I spray around the forward ground level exits, the forward lav, and the galley areas. I then head down the aisle, spraying near the floor level in bursts between passenger rows (to minimize any discomfort to the pax). In the back of the plane again I spray the around the ground level exits, the galley and the lavs.
This usually uses up most of the two full cans of spray, which is the requirement for the 737-800. I’ll usually have a little bit of pressure in the cans, which I’ll just discharge into a garbage.
But the other day I still had quite a bit left when I got to the back of the plane. One of the lavs was occupied, so I sprayed extra into the other lav while I was waiting.
I’m still waiting on the back galley when suddenly I hear a loud chiming noise “Ding! Ding! Ding! Ding! Ding!…” I look around and see the lavatory notification light is blinking. The smoke detector is going off. Immediately I know what’s happened. I open the lavatory door and see the space is still fogged with the insecticide, and it’s gotten into the smoke detector which sensed the tiny particles. The alarm is still going off, “Ding! Ding! Ding! Ding!”. All the passengers are looking back at me trying to figure out what’s happening. I’m fanning the lav with it’s own door and repeatedly trying to flush the toilet, trying to use the suction from it to get rid of all the fog.
After what was probably only a few seconds, I realize I need to call the forward galley, and have that flight attendant inform the flight deck what’s happening. I press the call button on the interphone, but I can’t hear it “ring”. The ringing on the interphone is a “ding dong” chime in the cabin, but with the consistent “Ding! Ding! Ding!” from the smoke detector I couldn’t hear it.
However both the flight attendant and the pilots were already on the line. They’d been calling me and I couldn’t hear it. As soon as I said, “Hi, it’s Jet” the pilot said, “We have a fire indication in the flight deck! What’s going on?!”
I proceeded to explain the spray and the lav, which raised a whole bunch of other questions. “Why are you spraying the cabin? Why the lavs? Shouldn’t that be done before the flight?”
“Are you sure there’s no fire!? Jet, ARE YOU SURE?”
“Yes, I’m looking into the lav right now! There’s no smoke, only fog. And it’s dissipating.”
During all this the spray fog has begun to dissipate the the alarm was stopping. It went through a short period of stopping and restarting, but after a minute it finally shut off when it stopped sensing any particles in the air.
I continued to explain and reexplain the the procedure. We must spray the entire aircraft, including galleys and lavs, after the doors are closed and before we land into Cuba. Apparently the pilots have never been made aware of this.
After it was all over and I hung up the interphone, and looked into the cabin. Everyone was looking back at me.
Silently I picked up my bug sprays and used up the remainder of the cans doing short bursts up the aisle, into the forward galley, where I closed the curtain behind me. The pax went back to watching their movie.
All the while I’m thinking, “how am I going to explain all this in my flight report?”.
I ended up submitting a single line;
“Insecticide set off smoke detector.”