How long does in take for Duct Mastic to dry

Our A/C unit was fixed today and the A/C guy said that we could turn on our unit right away. I said that shouldn't the mastic be allowed to set up? He said no, you can go ahead and turn on your A/C.

I believe that Mastic should at least set up for 24 hours. Is this correct?

Thanks,
Doug

Dry enough

I just used some the other day, (on that return duct work) and after about an hour, it was dry. I would say your ok, unless they had to fill a 3 inch hole with it...LOL

Mike

mastic

I would assume by now that it is hard enough to turn the unit on.