Do fire detection beam detectors work through glazing?

[Chris Houston]

Do fire detection beam detectors work through glazing?

[Colin Newman]

Not usually.

Most beam detectors transmit Infra-red signals.  Glass absorbs infra-red and re-emits it at a different frequency (aka the greehnouse effect).  This can confuse some beam detectors.  In additition any impurities or flaws in the glass can cause problems.

Another potential problem is if dust or condensation collects on the glazed surfaces since this may cause spurious alarms.