Does my air purifier make ozone? CARB's 0.050 ppm limit, the Mechanical or Electronic column, and the ionizer modes EPA names

Do not trust the words “ozone-free” on a box: the one thing to check is a column on a government list, and the Type it prints decides this page for you.

Does your air purifier make ozone?

The technology inside answers it, not the brand. EPA’s Guide to Air Cleaners in the Home names four technologies that may have the potential to emit ozone; its technical summary adds the lamp detail behind UV and PCO.

EPA’s ozone generators page adds that some ozone generators are manufactured with an ion generator or ionizer in the same unit, so an “ionizer” label alone does not settle which you own.

What does the CARB listing tell you?

CARB’s list is one searchable table with the columns Brand, Model Name, Model Number, Type, Date Notified and EO Number. Search the Model Number, because CARB files revisions of one product under different codes: the bedroom and living room review found Levoit’s Core 400S listed Mechanical and its LAP-C401S-WUSR code listed Electronic.

The list page states that to be certified, all air cleaners must be tested for electrical safety, and electronic air cleaners must also be tested for ozone emissions and meet an ozone emission concentration limit of 0.050 parts per million (50 ppb). The regulation text says the ozone figure is determined using Section 37 of ANSI/UL Standard 867; mechanical-filtration-only devices are excluded from the ozone test on the basis of de minimis emissions and carry the ANSI/UL 507 mark instead.

Rows read on CARB’s list on 2 October 2026. An Electronic row means the unit tested at or below 0.050 ppm; only a Mechanical row means no ozone and no ions by CARB’s definition.

What does 0.050 ppm mean next to the other limits?

EPA’s ozone generators page prints the reference points: the FDA requires ozone output of indoor medical devices to be no more than 0.05 ppm, OSHA limits workers to an average of 0.10 ppm over 8 hours, NIOSH recommends an upper limit of 0.10 ppm not to be exceeded at any time, and EPA’s outdoor National Ambient Air Quality Standard is a maximum 8-hour average of 0.08 ppm. CARB’s 0.050 ppm emission limit sits at the FDA figure.

UL 2998 is a different thing. UL’s page describes ULE 2998, the Environmental Claim Validation Procedure for Zero Ozone Emissions from Air Cleaners, as a validation that ozone stays below a quantifiable limit of detection of 0.005 ppm (5 ppb), one-tenth of the 0.050 ppm regulatory requirement. The CARB regulation text does not mention UL 2998, so “CARB certified” and “UL 2998 zero ozone” are two separate claims; a listing may carry one, both or neither.

Why can you not buy an ozone generator in California?

Title 17 CCR section 94802 reads: no person shall sell, supply, offer for sale, or introduce into commerce any indoor air cleaning device for use or intended for use in occupied spaces unless the device is certified by ARB to produce an ozone emission concentration not exceeding 0.050 ppm and is labeled as required. An intentional ozone generator cannot meet that, so it cannot be certified for occupied spaces; the regulation’s only ozone-generator carve-out is for devices sold solely through industrial outlets and labeled for industrial use.

CARB’s consumer page says the certified label reads “Meets California ozone emissions limit: CARB certified” beside the mark for ANSI/UL Standard 507, 867 or another appropriate standard, that certification has been required since 2010, and that an uncertified device sold online must state “Does not meet California air cleaner regulation requirements: cannot be shipped to California”. It names the marketing phrases to recognise: “super-oxygenated air”, “energized oxygen”, “activated oxygen”. CARB’s fact sheet puts it in one sentence: you should never use an air cleaner that deliberately produces ozone.

How do you switch the ionizer off?

Only as the maker’s manual states it. The Winix 5510/5520 user manual lists item 08, the PlasmaWave button: “Enables or disables PlasmaWave. Press the PlasmaWave button when the unit is on to enable or disable this feature.” A PlasmaWave indicator on the display shows whether it is enabled, and Sleep Mode disables PlasmaWave, which can be turned back on. The manual’s safety section states the product complies with the maximum allowable concentration of ozone of 0.050 ppmv in a 24-h period, and Winix’s product page prints an 8-hour TWA ozone figure of 0.22 ppbv in a 30 m3 chamber: Winix’s test, not OwnerSpec’s.

The Blueair Blue Pure 211i Max and the Coway AP-1512HH are also listed Electronic, but their manuals were not read for this page, so no switch-off instruction is given for them. A CARB Mechanical unit has nothing to switch off.

What should you do first?

1. Find the model number on the unit’s label, not the name on the box.
2. Search CARB’s list by Model Number and read the Type column: Mechanical or Electronic.
3. If Electronic, open the manual and find whether the ion, plasma or UV mode has its own button.
4. If the device is not on the list and is sold for occupied spaces, EPA’s and CARB’s wording on ozone generators is the answer.
5. Buying new: check the row before the price, then run the deal check on the CADR.

Frequently asked questions

Sources

1. CARB, List of CARB-Certified Air Cleaning Devices (government or regulatory source)
2. CARB, Air Cleaner Information for Consumers (government or regulatory source)
3. CARB, Air Cleaning Devices for the Home (fact sheet) (government or regulatory source)
4. CARB, Regulation for Limiting Ozone Emissions from Indoor Air Cleaning Devices, Title 17 CCR sections 94800 et seq. (PDF) (government or regulatory source)
5. EPA, Guide to Air Cleaners in the Home (government or regulatory source)
6. EPA, Ozone Generators That Are Sold as Air Cleaners (government or regulatory source)
7. EPA, Residential Air Cleaners: A Technical Summary, 3rd edition (PDF) (government or regulatory source)
8. UL Solutions, Zero Ozone Emissions Validation (ULE 2998) (standards or certification body)
9. Winix America, 5510/5520 User Manual (PDF) (manufacturer or vendor document)
10. Winix America, Winix 5510 product page (manufacturer or vendor document)