Sweating copper and fires in wall cavities. How much smoke is worrisome?

Sweat noob looking for advice on fire safety. How much smoke is normal when sweating? And for how long should I still be seeing "expected" smoke? Lame story to follow

Yesterday I'm sweating a new fitting for a shower valve, inside a small access panel, on the shower head pipe. I have a license plate behind it as a fire barrier. Fitting is high in the opening and I can't see much above it (see diagram).

After finishing I see a little smoke rolling out from the cavity (like a lit cigarette's amount). I'm alarmed but I wait for what FELT LIKE 2-3 minutes before I go full panic. Smoke is still trickling out and now I'm having visions of my house in flames, I grab the extinguisher and blast that shit up the cavity. Now there's extinguisher bullshit floating in the air and I can't tell if there's any more smoke, so I start hulking the drywall off the studs with my bare hands and I never find anything.

Any pro tips here? Is this a crazy overreaction? How much smoke do you guys expect in the field? Not sure what was burning, could it have been flux (I'm using propane), spider webs, fiberglass, flames shooting through the pipe melting my showerhead? I'm a disaster