Yeah, unless you need to stay silent for detection reasons or warfare, my guess would be that in a fixed facility, it would be way cheaper and reliable to have

Yeah, unless you need to stay silent for detection reasons or warfare, my guess would be that in a fixed facility, it would be way cheaper and reliable to have a positive pressure or flow of air going outward. I've seen windows and buildings do this completely passive, so a modern design would only have this as an absolute emergency, as they are dangerous and doesn't solve the Co2 problem. Don't see how this is relevant for civil use though, but hey, maybe some paranoia can sell some candles.