Would it be normal for a small/medium sized moth to be able to set off a PIR? The alarm went off just as we went to bed and upon entering the room/zone which had been triggered there was a moth sitting next to the PIR. I assume that it just happened to fly next to the PIR so to the detector it looked like a big moving object in the room. Is there anything I can do to prevent false alarms like this?

Thanks.

It's cetainly possible, for the reason you described. It may have landed on the sensor.

There's not much you can do about it really

I had one customer who used one of those 'pritt stick' type insect repellant sticks and wiped it all over the pir's, including the lenses !

It just made them go all sticky and a funny brown colour, we had to change them all eventually as they did not detect anymore.

I stand corrected!

Yes agree it is possible. Also this time of year we are plagued with daddy long legs witch also set of PIRs.

OK, thanks all. At least you've confirmed that it's not a problem with my system setup.

LOL @ Norman's pic - that thing looks like it could set off a PIR all by itself!!!

Just to add - it makes sense to dust around each movement detector and remove any cobwebs with some regularity (even if you really can't see them).

An insect walking across the front of the detector will appear the same size as a human moving in the room, hence the false alarm. Spiders etc get attracted to the warmth and a tiny spider could get inside the detector (if it is not sealed 100%) and walk across the lens every morning at 3am.

used to get a few call outs to spiders in sensors or walking across lens.

The customer was always not convinced until i opened the cover and out ran the spider.

Used to get a few calls to fire systems by corn flies inside the detector chamber.

The customers think we are mad putting flea collars around the detector but it really works.

Moth balls work.

The detector will only see the moth/spider as something big if it got close enough. Because moths etc dont like the smell of Moth balls they dont go near.

The downside is your house will smell like an old lady's knicker draw. (not that I would know what an old lady's knicker draw would smell like)

Pete