Hi peiyng27,
I dont understand what is mean inside the ceiling? You have artificial ceiling and you want to put the glue trap under the ceiling - in the distance between the roof and the artificial ceiling?
If i understood right and the case is this - i think it is not a problem to put it. Of course you should make hazard analysis of this because only based on few words nobody can told you it is safety or not.
Why you dont thing in other way - about prevention. Make investigation and trend analysis to see were the pest activities are more, when they are increase, what is that place/s.... After that based on this trend analysis and finded the root cause you can increase the baits which are outside or maybe will be better to take and some other preventive actions based on the cause (e.d. if the place where activities are increase is near to the waste containers you can shose to take off more often the waste...)
The good practice is to be putted 2 cordons baits outside - one trought to the wall which cover your area and second around the buildings. Where have a door is good practice baits to be puted to the both sides (left and right) and many many other things. There are many guidances about the pest control.
Have a nice day.
Best regards,
Ivan