NBC Air Filtration Systems, Compared on Published Figures

An NBC filtration unit is the piece of a shelter that decides whether the room works. It draws outside air through particulate and carbon stages and holds the room at positive pressure, so contaminated air cannot leak in through gaps.

It is also a category with very few real products and a great deal of loose marketing. Below are the systems whose numbers are published by the people who build them.

The comparison

Reading these numbers

The 550 in Air550 is not an airflow. It is a model name. Castellex rates the unit at up to 150 m³/h^[1], which is roughly 88 CFM. Any comparison that treats the model number as a flow rate will put it in the wrong class entirely.

Occupancy ratings are not comparable between makers. Castellex rates the Air550 for up to 24 people at 150 m³/h^[1]. Lunor rate the VA-40 at 40–80 m³/h for about 13 occupants — and tie it to a room area, up to 15 m²^[4]. American Safe Room sells a 120 CFM unit, about 204 m³/h, and publishes no headcount at all^[2].

Read those three together and the problem is obvious. Castellex claim nearly twice Lunor's headcount on the same airflow. Lunor are the only one tying the number to a room size, which is the variable that actually determines it. There is no shared standard behind “rated for X people,” so buy on airflow and work the headcount out against your own room volume.

Manual backup is the specification that matters most. The scenario these units exist for is the one where the grid is down. The Safe Cell complete system ships with a hand crank and two 7 bar blast valves^[2]; the Castellex listing publishes neither. That is a difference in what you are buying, not a difference in quality.

Recommendation

The Castellex is the more elaborate filter train and publishes a 99.995% efficiency figure^[1]. It is also priced in sterling, ex-VAT, from the UK — so a US buyer is importing a £7,450 unit before shipping and duty. That is worth knowing before the spec sheet talks you into it.

Swiss systems, and how to actually buy one

Switzerland has mandated shelter provision for decades, so Swiss equipment is the reference point in this category. Two names come up.

Lunor build the VA series — VA-40, VA-75, VA-150 and VA-300, scaling from around 13 occupants to 200^[4]. It is sold in the US through Bomb Shelter Supply with a listed price, which makes it the one Swiss system you can price without a phone call. Stock moves, so expect to ask about lead time.

Andair AG of Andelfingen is the other. There is exactly one US distributor — Andair USA in St George, Utah, which shares its people with Utah Shelter Systems^[3]. Everything is quoted by phone and nothing is published, which is why no Andair unit appears in the table above.

If you are not building a room yet

A filtration unit only does anything once there is a sealed room to pressurise. If you are earlier than that, personal protective equipment is the part of this category you can actually buy today.

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The CM-6M takes standard 40 mm NATO thread filters, which is the fitting most CBRN cartridges are made for. A respirator protects a person, not a room — it is a different purchase from anything in the table above, not a cheaper version of one.