Danger from sewer gas when soldering copper drain?

[Travelover]

I need to repair a copper drain in an upstairs bath by re-sweating a fitting. The house has a septic system with properly vented plumbing stacks through the roof. Is there a danger of igniting sewer gases when sweating this fitting?

Thanks in advance.

[David L. Martel]

Trav,

The trap should be blocking the sewer gas. Is it working? What do you smell?

Dave M.

[HeyBub]

What do you think would happen if the sewer gas DID ignite?

[Tom]

Dave, I'm downstream from the trap, in the wall. I don't smell any sewer gas.

[Stormin Mormon (on backup com]

BOOM!!!!