I met an NTSB investigator who said they carried a trash bag with them on flights so they could grab a bag full of fresh air to breath and buy time if smoke or noxious fumes filled the cabin. Don’t know if they ever had to do so. Not sure how well it would work either, or maybe they developed cautious behavior due to their job.
They also said that pilots would often let them get a good look from the air as they were arriving to let them get a better understanding of the scene.