Air purification, and what each technology can honestly do
This is the corner of the trade with the loudest marketing and the thinnest evidence. Some of it works well at a specific job. Some of it works at a different job than people assume. And a few products make claims that are still being argued over. Here is what each one actually does.
Purification is the third step, not the first
Before adding equipment, three things determine most of the air quality in a house, and all three are cheaper to fix.
- Source. Standing water in a crawlspace, a bathroom fan venting into an attic, a damp basement. No purifier removes a source, and equipment installed around one is money spent on a symptom.
- Airflow. Filtration only works on the air that passes through it. A system with restricted returns or a filter too dense for it moves less air and therefore cleans less air, whatever the rating on the box.
- Ventilation. Filtering removes what is in the air. It does not replace stale air with fresh. A sealed house that feels stuffy needs air exchange, not another filter.
We check those first. In a good share of houses, correcting filtration and return air resolves the complaint for a fraction of what equipment costs, and we would rather tell you that on the visit than sell you a purifier that underperforms because the airflow was never right.
What each one does, and does not
Most whole-home systems combine two or three of these. Knowing which part is doing which job is how you avoid paying for something that does not address your actual complaint.
Deep media filtration
A four or five inch filter cabinet fitted into the return, replacing the one inch slot filter. This is the single most effective air quality upgrade in most homes and the one we recommend first.
Does
- Captures dust, pollen, pet dander and smoke particles by size
- Far more surface area, so higher filtration without choking airflow
- Lasts six to twelve months instead of one to three
- Protects the coil and blower, which protects efficiency
Does not
- Remove gases, odors or VOCs, which pass straight through
- Help with humidity in either direction
- Work on air that never reaches it, so returns still matter
- Fit every system without a duct modification
UV-C on the coil
A germicidal lamp aimed at the evaporator coil and drain pan. Worth being precise about this one, because it is frequently sold as an air treatment when its real value is a surface treatment.
Does
- Keeps biological growth off a coil that stays wet all summer
- Helps with musty smells originating at the coil and pan
- Keeps the coil cleaner, which preserves airflow and efficiency
- Runs continuously with no filter to change
Does not
- Meaningfully treat air passing by at duct speed, since exposure is a fraction of a second
- Remove particles, so it is not a filter replacement
- Last forever. Lamps fall below useful output while still visibly glowing
- Address odors originating anywhere other than the coil
Activated carbon
A carbon layer, usually combined with media filtration, that adsorbs gas-phase contaminants rather than trapping particles.
Does
- Reduces odors, including cooking, pets and smoke
- Adsorbs some volatile organic compounds
- Pairs naturally with a media cabinet, covering both particles and gases
Does not
- Last indefinitely. Carbon saturates and then stops working with no visible sign
- Capture particles on its own
- Replace fixing an odor source, which is always the better answer
Ionization and PCO systems
Products that treat air with ions or photocatalytic reactions rather than capturing anything. This category makes the broadest claims in the industry and has the most contested evidence behind it.
What is claimed
- Manufacturers report reductions in particles, odors and pathogens
- No filter to change and low ongoing cost
- Fits into existing ductwork easily
What we tell customers
- Independent results have been mixed and often well below manufacturer testing
- Some designs can generate ozone or reaction byproducts as a side effect
- Laboratory chamber conditions are not a working house
- We will fit one if you want it, and we will not lead with it
What would actually help
Pick what is bothering you and we will tell you which technology addresses it, and which ones will not.
Technology matcher
Honest guidance rather than a product recommendation. Some of these have answers that cost nothing.
Nothing here is medical advice. If symptoms are health related, a doctor is the right first call. What we can tell you is what the equipment does and what the building is doing.
How it goes in, and what we check first
Whole-home equipment fits into the return or supply, which means it interacts with the airflow the entire system depends on. Getting that wrong makes the heating and cooling worse.
- Static pressure measured before anything is chosen. This tells us how much filtration the system can carry. Skipping it is how houses end up with frozen coils in July after an air quality upgrade.
- Return air assessed. Undersized returns are the most common duct fault we find, and they cap what any filtration can achieve.
- Cabinet sized and located so the filter can actually be changed without dismantling anything. Filters that are awkward to reach do not get changed.
- UV lamps positioned for coil coverage rather than dropped into the duct where they do little.
- Service intervals written down. Media, carbon and lamps all have a service life, and a purifier past its service life is a restriction rather than an improvement.
- Commissioned and rechecked. Static pressure and airflow measured again afterwards to confirm the system still breathes properly.
Air purification questions
Tell us what you are noticing
What the problem is, which rooms, and whether it changes with the season. We will measure the airflow before recommending anything.
Next steps and neighbors
Get the airflow measured first
We check static pressure, returns and filtration before recommending equipment, and we will tell you when the answer costs nothing.