An adapted version of the Number 6 AFU called Number 7 AFU, is constructed of low magnetic materials, which makes it more suitable for use in mine-countermeasure vessels and similar environments that demand low magnetism. Like the number six the unit has a maximum airflow rate of 340 m3/hr.
- Each Number 7 Air Filtration Unit consists of three filters:
- A Pre-filter, which removes coarse particulate matter down to 5 microns, including nuclear fallout.
- A HEPA Filter, which removes fine particulate matter down to 0.3 microns, including bacteria.
- A Gas Filter, which removes chemical and radiac warfare agents in the form of gases or vapours by adsorption to the activated charcoal filling.
- A MK2 version increases the flow by 50% with a small increase in equipment envelope.