The core hardware of a premium nuclear bunker air scrubber (like those from DEFCON Bunkers or [American Safe Room]) lasts 5 to 10 years. However, the actual CBRN filters (gas and particulate) require replacement every 6 to 12 months when operating, while the primary HEPA filter can last for years in dry, non-contaminated environments.
They could do like submarines and have air scrubbers. That’d keep them going for a while with no vents.
The core hardware of a premium nuclear bunker air scrubber (like those from DEFCON Bunkers or [American Safe Room]) lasts 5 to 10 years. However, the actual CBRN filters (gas and particulate) require replacement every 6 to 12 months when operating, while the primary HEPA filter can last for years in dry, non-contaminated environments.
Bunker air filtration : r/preppers https://share.google/1ocXyhrcvc9nSWYoc