I couldnt find any hvac putty, will Fire Block FB 136 work just as good. This is being used for sealing several leaks in our hvac system.
Are you trying to seal connections between your duct work? If so, then consider using duct mastic. This is what professionals use.
Here is a link with a video on how to use it.
Here is a link that might be useful: How to Seal Ductwork
In our garage is a box with a hot & cold line going into it. I think its where the ac coils are.? Where the lines go in & on the corners there are small air leaks. I just need something that can handle heat & cold & fill very small holes/cracks. I could not find what my father suggested, hvac putty, I was told fire block fb 136 would work, but I dont trust them.