Of course, only use this cap, when your lasercutter is not active!

A cap for the loose end of your Mr Beam lasercutter, to keep bad odor in the hose, when it's not connected to the filter or other exhaust systems e.g. for transport or storage.

I made two versions. One plain version and one with a handle to hang a sign on it, like the one below, if you want an reminder to reconnect the hose somewhere before lasering. ;-)
If you want to make it fool-proof, hang the start-key of the cutter to the handle. 
https://www.printables.com/model/679267-remove-before-use-sign 

I've printed it with 3 perimeters, PETG.