Overview
Disposable carbon / potassium permanganate air filter, 1" × 18" × 18". Phoenix part number 4031878.
It is the odour and gas-phase stage in a Guardian R air scrubber — the filter that removes what a particulate filter cannot.
What it fits
- Phoenix Guardian R air scrubber — named in the Guardian R Pro 50 Hz service parts list under Optional Parts, Air Filter, Disposable Carbon / Potassium Permanganate
What it actually does
HEPA filters remove particles. They do nothing to odour, because odour molecules are gas-phase and pass straight through. That is why a room can be scrubbed to a HEPA standard and still smell.
This filter addresses that in two ways:
- Activated carbon adsorbs a broad range of volatile organic compounds — smoke, solvent and general odour molecules stick to the enormous internal surface area of the carbon.
- Potassium permanganate is an oxidiser, and it handles the compounds carbon is weak on — hydrogen sulphide, formaldehyde and light sulphur compounds. It is the reason this media suits sewage and protein odour work as well as fire work.
Important — media exhausts, it does not block
This is the difference between a gas-phase filter and a particulate one, and it catches people out.
A pleated filter tells you it is finished: airflow falls, the machine works harder, the media looks loaded. A carbon filter gives you none of those signals. When the adsorption sites are full it simply stops working, at full airflow, looking exactly as it did on day one.
Judge it by odour performance and by exposure, not by appearance. If the scrubber has stopped touching the smell, the media is spent regardless of how it looks.
Potassium permanganate media does give one clue: it is normally purple when fresh and turns brown as it is consumed. Where you can see the media, use that.
Use it as a stage, not a substitute
Fit it behind the pleated pre-filter (4031877), not instead of it. Loading a carbon filter with bulk particulate wastes expensive media on work a cheap pre-filter should be doing.
The full Guardian R stack is pre-filter (4031877) → carbon / permanganate (4031878, optional) → HEPA 4031864.
Frequently asked questions
Does it replace the HEPA filter?
No. It does a different job — HEPA removes particles, this removes odour. Use both.
Can I regenerate or wash it?
No. It is disposable, and washing destroys the media.
How long does it last?
It depends entirely on the odour load. There is no meaningful hour figure. Judge by performance.
Do I need a pre-filter as well?
Yes, and it will save you money on this one.
Working a difficult odour job? Tell us what you are dealing with and we will talk through whether carbon media, a hydroxyl or ozone approach, or a chemical counteractant is the right tool — they are not interchangeable.
