Whole-Home Air Purification
Clean air in every room the ductwork reaches, not just the one with a box in the corner. Filtration first, sized so your system can still move air — and every device checked against California's certified list.
Three approaches, and what each is actually good at
These get sold as though they are interchangeable. They are not, and the evidence behind them is not equally strong either.
High-MERV media filtration
A deep filter cabinet with far more surface area than the one-inch slot filter most homes have.
Best at
Particulates — dust, pollen, and the fine particulate that wildfire smoke is made of.
Our honest view
The best-evidenced approach by a wide margin, and where we start in almost every home.
UV-C in the air handler
Ultraviolet light aimed at the evaporator coil and drain pan.
Best at
Keeping biological growth off the coil itself, which is a real maintenance benefit.
Our honest view
Genuinely useful for coil hygiene. Treat claims about sterilising the air passing by at duct velocity with more caution.
Electronic and ionising devices
Charge or react with particles and compounds in the airstream.
Best at
Marketed for odours and compounds that filters do not capture.
Our honest view
The category where certification matters most. Any device installed in California has to meet the state ozone limit — we check the list before specifying anything.
Air cleaners sold in California have to be certified
This is the part of the conversation the industry tends not to raise, and it is worth knowing before anyone sells you a device.
California regulates ozone emissions from indoor air cleaning devices. Equipment sold or shipped into the state must be certified for both electrical safety and ozone emissions, and certified products carry a label saying so. The state publishes the full list of certified devices.
What the rule requires
- An ozone limit of 0.050 parts per million for certified devices.
- Electrical safety testing in addition to the ozone requirement.
- In-duct electronic devices included since October 2020 — which is precisely what a whole-home purifier is.
- A label on the packaging stating that the device meets the California ozone emissions limit.
Why it matters practically: ozone is a lung irritant, and a device that produces it while claiming to clean your air is working against the thing you bought it for. The certification exists precisely because some products did.
We specify from the certified list and will show you the entry for whatever we propose. It is a two-minute check, and a surprising number of installers do not make it.
A better filter can make things worse
The instinct when air quality is the concern is to fit the densest filter that will physically go in the slot. It is the wrong move, and it is common enough to be worth stating plainly.
A dense filter in a standard one-inch slot restricts airflow. That raises static pressure across the system, costs you heating and cooling capacity, stresses the blower motor, and in cooling can drop the coil temperature far enough to freeze it.
The answer is more filter area, not denser filter media. A deep media cabinet has many times the surface area of a slot filter, so it can filter finely while presenting far less resistance to airflow.
Which is why we measure static pressure before specifying filtration. If your system is already fighting for air, adding restriction is the last thing it needs — and that measurement tells us before we make it worse.
Filtering is step four of five
Each step makes the next one work. Done out of order, you spend more and get less. See the whole process.
- 1 Identify
Measure before buying anything, so you treat the problem you actually have.
Air quality testing → - 2 Remove
Clear genuine contamination out of the ductwork, where conditions warrant it.
Duct cleaning → - 3 Seal
Close the route unfiltered attic air uses to get back into the system.
Duct sealing & replacement → - 4 Filter
Filtration that works, because the air reaching it is the air you meant to treat.
You are here - 5 Ventilate
Dilute what filters cannot catch by replacing indoor air with outdoor air.
Whole-home ventilation →
Before you fit a denser filter
Static pressure is the measurement that tells you whether your system can take more filtration at all.
Why Is My House So Dusty Even After Cleaning?
Dust that returns within days is usually being pulled in through leaking ducts, not settling out of the room.
Read the article →HRV vs ERV: Which One Makes Sense in a Dry Climate?
Most HRV vs ERV advice is written for Canada. The answer is different in a hot, dry climate — and so is the plumbing.
Read the article →The 'Static Pressure' Secret: Why Your HVAC System is Suffocating
The most common reason an AC runs all day without cooling has nothing to do with refrigerant.
Read the article →Air Purification FAQs
Do air purifiers sold in California have to be certified?
Yes. California limits ozone emissions from indoor air cleaning devices, and equipment sold or shipped here must be certified against that limit. Since October 2020 the rule has also covered in-duct electronic devices, which is exactly what a whole-home purifier is.
What is the CARB ozone limit for air cleaners?
Certified devices must not exceed an ozone concentration of 0.050 parts per million, and must also pass electrical safety testing. Certified products carry a label stating that they meet the California ozone emissions limit, and the state publishes a searchable list.
What is the best type of whole-home air purifier?
For most Los Angeles homes, a properly sized high-MERV media filter cabinet. Filtration is the best-evidenced approach for particulates, which is what wildfire smoke and household dust actually are. Everything else is a supplement to that rather than a replacement.
Will a whole-home purifier help with wildfire smoke?
Good filtration genuinely helps, because smoke is fine particulate and that is precisely what a filter captures. What matters as much is how much unfiltered air leaks in around it, which is why we look at duct sealing alongside filtration.
Is a portable purifier as good as a whole-home system?
A good portable unit works well in the room it is in, and that is a genuine option for a bedroom. A whole-home system treats every room the ductwork reaches, which is the difference that matters when the outside air is bad everywhere.
Can a high-MERV filter hurt my HVAC system?
It can if the system was never designed for the added resistance. A dense filter in a small slot raises static pressure, costs capacity and stresses the blower. The fix is more surface area rather than a denser filter, which is what a media cabinet provides.
Does UV-C actually do anything?
It has a real and well-understood use keeping biological growth off the evaporator coil and drain pan, which is a genuine maintenance benefit. Claims about disinfecting air moving past at duct velocity deserve considerably more scepticism than they usually receive.
How do I know the equipment you install is compliant?
We specify from the state's certified list and can show you the entry for whatever we propose. It is a two-minute check that a surprising number of installers skip, and it is the difference between a compliant device and an uncertified import.
Get it specified properly
Tell us what you are trying to solve. We will measure your airflow before recommending anything that restricts it.
Sources
The code requirements and thresholds on this page come from the following. All are public — check them yourself.
California Air Resources Board
California's Air Cleaner Regulation (AB 2276)Ozone emission limit and the requirement that air cleaning devices sold in California be certified.
California Air Resources Board
List of CARB-Certified Air Cleaning DevicesSearchable list of certified equipment.