: These are standard for firefighting. You breathe in compressed air from a tank on your back and exhale it directly into the atmosphere. They are simple and reliable but limited by the tank's capacity, typically providing about 30–45 minutes of air.
: These recycle your breath. A "scrubber" removes carbon dioxide, and sensors add fresh oxygen back into the loop. This is much more efficient—a 2-liter tank on a rebreather can last up to 8 hours, compared to just 1 hour for a standard scuba tank. 2. Evolution of Firefighting Tech breathing apparatus
The history of firefighting BA highlights some strange early attempts: : These are standard for firefighting