This is my point. Passenger oxygen masks are not designed nor intended for smoke protection. Most SOP's clearly state to not deploy passenger masks during fire or smoke. They will not prevent the wearer from inhaling smoke and fumes, and can cause the situation to become worse.
The best a crew can do is keep the passengers calm and perform the smoke removal procedure if it becomes the biggest threat. If the bleed from the engine isnt contained by pushing the fire handle or pack is belching toxic fumes - the packs and bleeds need selected off and open the ram air and raise the cabin. Deploying 140 passenger masks with chem generators isn't going to do diddly squat.