Some Rosco smoke machines have an air inlet for compressed air cleaning.

Most manufacturers recommend flushing the machine through with distilled
water occasionally, just run with distilled water instead of smoke fluid
(this isn't for compressed canister guns...).

Rosco's instructions for the 1500 say to run the unit without fluid
until nothing comes out, then run distilled water through it, and again
to run it until it nothing comes out before putting it away. (When
storing the unit, it should be dry inside to prevent corrosion and
"gunking up".)

If the output is weak, sputtering or not straight you may need to unclog
the nozzle. Unbend a large paper clip and use it to ungunk whatever is
in the nozzle hole. DISCONNECT THE MACHINE AND ALLOW IT TO COOL FIRST!

Check with your manual, or your local dealer.