Indoor Air Rules Shifted in 2025-26. What It Means for Your Home

California's updated energy code took effect on January 1, 2026, keeping tested range hood minimums for newly built homes, and ASHRAE's 2025 home ventilation standard tightened filtration and exhaust rules. Federal regulators moved the other way: the Consumer Product Safety Commission's acting chairman said in February 2025 that the agency has no plans to ban gas stoves, and a March 2025 GAO report notes there are no federal indoor air quality standards for homes. For an existing home nothing new is required, so protection still comes from what you do: a radon test, working carbon monoxide alarms, a range hood you switch on, and humidity kept in check.

Key takeaways

EPA's 2025 radon guide keeps the action level: fix your home if a long-term test shows 4 pCi/L or more, and consider fixing between 2 and 4. Nearly 1 in 15 US homes has elevated radon.
A Stanford-led study estimates that gas and propane stoves add about 4 parts per billion to long-term nitrogen dioxide (NO2) exposure on average, 75% of the WHO's annual guideline, and four times as much in homes under 800 sq ft as in homes over 3,000 sq ft.
In a new California home of 1,001 to 1,500 sq ft, a hood over a gas range must capture 80% of emissions in a standard test or move 250 cubic feet per minute (cfm); over an electric range, 50% or 110 cfm.
EPA advises indoor humidity below 60%, ideally 30% to 50%, and drying leaks within 24 to 48 hours.
No federal limit applies to carbon dioxide (CO2) in homes. ASHRAE says CO2 readings are not overall indicators of indoor air quality; its standards dropped a 1,000 ppm limit after the 1989 edition because it was widely misread.

What it means for you

Homeowners: no new rule applies to an existing house. Test for radon, put CO alarms on every level, and use fans that vent outdoors.
Renters: you can test, use the hood and run bathroom fans; a radon system or new ducting needs the owner's approval, so ask in writing with your results.
People cooking on gas: run the hood every time, favor the back burners, and open a window when you can.
Households with young children, asthma or older adults: EPA links NO2 to airway reactivity in some people with asthma and respiratory infections in young children. The CDC says infants, older adults and people with heart disease, anemia or breathing problems are more likely to get sick from CO.
Buyers of new California homes permitted from January 1, 2026: the kitchen needs vented exhaust that meets the table below.

This article is general information, not medical advice. If a CO alarm sounds, or someone has a headache, dizziness or confusion that could be from CO, get everyone into fresh air and call 911.

What changed in 2025 and 2026

The new attention comes from codes, standards groups, states and researchers; federal regulators have pulled back. Each item was checked on October 4, 2026, against the issuer's document or the source named.

Date	What changed	Status as of October 4, 2026
Jan 11, 2024	HUD Notice CPD-23-103: radon must be considered in environmental reviews of HUD-assisted projects	In effect since April 10, 2024. Notice CPD-2026-001 (January 9, 2026) moved the start for Tribes and Hawaiian Home Lands to May 11, 2026.
Feb 12, 2025	ASHRAE revises its position document on indoor carbon dioxide	Current until February 12, 2028.
Feb 26, 2025	In a letter printed in a GAO report on gas stoves (March 18, 2025), CPSC Acting Chairman Peter Feldman writes that CPSC has no plans to ban gas stoves or pursue other mandatory standards that would limit consumer choice, and that he considers its 2023 request for information on gas-range hazards "concluded"	No CPSC gas-stove rulemaking found. Voluntary test-method work continues, per GAO.
2025	ASHRAE Standard 62.2-2025 for home ventilation: filtration rises from MERV 6 to MERV 11, toilet rooms need local exhaust, and air cleaners get ozone requirements	Voluntary; binding only where a code adopts it. California's code uses the 2019 edition.
2025	EPA A Citizen's Guide to Radon, 2025 edition	Current; action level and testing steps unchanged.
Jun 2025	The FY2026 EPA budget request proposes eliminating EPA's radon program and state radon grants	Not adopted. According to the radon industry group AARST, the House-Senate agreement announced January 5, 2026, kept both at FY2025 levels.
Jun 4, 2025	Colorado HB25-1161: retailers must put an air quality label on gas stoves on display and on product web pages	Took effect August 6, 2025, but the state agreed not to enforce it until a court ruled on appliance makers' First Amendment request for an injunction, and a federal court blocked enforcement on December 19, 2025. The case is still open.
Jan 1, 2026	California's 2025 Energy Code takes effect	Applies to buildings whose permit applications are filed on or after January 1, 2026. Multifamily ventilation rules are strengthened.

Radon: test, then read the result

Radon is a radioactive gas that seeps up from soil. EPA estimates it causes about 21,000 lung cancer deaths a year and is the leading cause of lung cancer among nonsmokers. The average indoor level is about 1.3 pCi/L (picocuries per liter of air), against 0.4 outdoors. Only a test tells you your level.

How EPA says to test

Short-term tests run 2 to 90 days; long-term tests run more than 90 days and better reflect the year-round average.
Use a regularly used room on the lowest lived-in level, not the kitchen or bathroom, with the kit at least 20 inches above the floor and away from drafts, heat, humidity and exterior walls.
For a 2- or 3-day test, close windows and outside doors 12 hours beforehand and keep them closed; skip severe storms and very high winds.

Illustrative example: two short-term results

EPA's steps: if a first short-term test reads 4 pCi/L or more, follow up with a long-term test, or a second short-term test for a quick answer. Above 8 pCi/L, twice the action level, do the second short-term test right away. Two hypothetical homes:

Home A: 9.0 pCi/L, then 7.0 right away. The average, (9.0 + 7.0) ÷ 2 = 8.0, is twice the action level; EPA says the higher the results, the surer you can be that fixing is needed.
Home B: 4.4 and 3.8, an average of 4.1. EPA says to consider fixing at 4 or more, but at 4.1 there is about a 50% chance the year-round level is somewhat below 4, so a long-term test gives a better read.

EPA also says no level of radon is safe. Systems can cut levels by up to 99%, most homes can get to 2 pCi/L or below, and installation usually costs about as much as other common home repairs. Your state radon office lists qualified testers and mitigators.

For HUD-assisted projects, Notice CPD-23-103 itself doesn't require testing (some HUD programs' rules do), but a test or area data showing 4 pCi/L or more means the environmental review must include a mitigation plan. It doesn't cover buying a home with an FHA single-family mortgage or a Section 184 or 184A loan guarantee.

Gas stoves, range hoods and CO

Burning gas indoors produces NO2, carbon monoxide and fine particles. EPA says NO2 irritates the eyes, nose, throat and airways, and that venting combustion sources outdoors is among the most effective protections. Two Stanford-led studies:

In 87 homes in California and Colorado (2023), gas and propane burners on high and ovens at 350°F emitted 10 to 25 times more benzene than electric coil or radiant cooktops; induction and the food itself emitted none detectable. In some homes, benzene reached bedrooms and stayed above chronic health benchmarks for hours.
The 2024 NO2 study, which paired measurements in more than 100 homes with a model, found short-term NO2 from typical use frequently exceeded WHO and EPA benchmarks. It estimates stove NO2 causes about 50,000 current cases of childhood asthma, a modeled figure; GAO notes meta-analyses disagree on how much of the gas stove and asthma link reflects NO2 rather than income or family history.

What a hood actually does

In five homes in the 2024 study, outdoor-vented hoods cut hour-averaged kitchen NO2 by 10% to 70%, 35% on average. In the authors' model, people who use a hood that captures 75% of emissions every time they cook get 70% less long-term stove NO2 than average, yet surveys they cite found hoods switched on only 15% to 39% of the time.

Hoods covering all burners capture more, and back burners vent better than front ones, GAO adds. In the 2024 study's model, opening windows cut long-term exposure about as much as average hood use but did far less for spikes during cooking.

Worked example: sizing kitchen exhaust

California's code adopts ASHRAE 62.2-2019 with state amendments and covers new homes whose permit applications are filed from January 1, 2026; existing homes needn't retrofit, though an addition of more than 1,000 sq ft must meet the whole-home ventilation rate. Capture efficiency (CE) is the share of a tracer gas released at the cooktop in a standard test that the hood removes directly. The state's 2025 compliance manual sets these minimums for vented hoods; a hood can meet either the CE or the airflow figure:

Home floor area	Hood over electric range	Hood over gas range
Over 1,500 sq ft	50% CE or 110 cfm	70% CE or 180 cfm
Over 1,000 to 1,500 sq ft	50% CE or 110 cfm	80% CE or 250 cfm
750 to 1,000 sq ft	55% CE or 130 cfm	85% CE or 280 cfm
Under 750 sq ft	65% CE or 160 cfm	85% CE or 280 cfm

Smaller homes get stricter minimums, since the same emissions mix into less air. A third-party rater verifies the hood's HVI or AHAM rating, including a 3-sone noise limit at a setting of at least 100 cfm; recirculating hoods don't count. An enclosed kitchen can instead use a 300 cfm ceiling or wall fan, or a continuous fan giving five air changes per hour. The manual's formulas:

Continuous kitchen exhaust (cfm) = kitchen volume (cu ft) × 5 air changes per hour ÷ 60 minutes
Whole-home ventilation, Qtot (cfm) = 0.03 × conditioned floor area (sq ft) + 7.5 × (bedrooms + 1)

Qtot is the total fresh air a home needs; California lets part of it come from natural air leakage, so the fan itself can be smaller.

Illustrative example: a 1,400 sq ft, two-bedroom home has an enclosed 12 × 10 ft kitchen with a 9 ft ceiling.

Kitchen volume: 12 × 10 × 9 = 1,080 cu ft. Continuous exhaust: 1,080 × 5 ÷ 60 = 90 cfm.
With a hood instead, a gas range here needs 80% CE or 250 cfm. At 250 cfm, the hood moves 250 × 60 ÷ 1,080 ≈ 13.9 kitchen volumes an hour while it runs; an electric range's 110 cfm works out to about 6.1.
Whole-home ventilation: 0.03 × 1,400 + 7.5 × (2 + 1) = 42 + 22.5 = 64.5 cfm.

In this home a gas range needs more than twice the hood airflow of an electric one (250 vs 110 cfm); in other size bands the gap is 1.6 to 2.2 times. The 64.5 cfm of background ventilation is spread across the whole home, so it doesn't replace a hood. Outside California, local codes differ, but the table is a useful yardstick when replacing a hood.

Carbon monoxide alarms

The CDC counts more than 400 US deaths a year from unintentional CO poisoning not linked to fires. The CPSC and NFPA advise CO alarms outside each sleeping area and on every level, with battery power or battery backup, ideally interconnected so that when one sounds, they all do. NFPA adds: follow the maker's mounting instructions and local code, and test monthly.

The CDC recommends yearly professional service of gas, oil or coal appliances. Never run a portable generator indoors or in a garage; keep it at least 20 feet from the house, exhaust pointed away from windows, doors and vents.

Moisture, mold and chemical fumes

EPA's mold guide advises keeping indoor relative humidity below 60%, ideally 30% to 50%. Run the bathroom fan while showering, use exhaust fans when cooking or running the dishwasher, and vent dryers outdoors. Materials dried within 24 to 48 hours usually won't grow mold, and a patch under about 10 sq ft is usually a DIY job. The WHO's dampness and mould guideline makes the same point: preventing persistent dampness matters most.

Volatile organic compounds (VOCs) are gases from paints, cleaners, adhesives and similar products. EPA reports that several average 2 to 5 times higher indoors than outdoors. EPA calls source control usually the most effective fix: buy only what you'll use soon, don't keep opened paint cans indoors, and ventilate while using these products.

Indoor sources of formaldehyde include resins in composite wood such as particleboard, medium-density fiberboard and hardwood plywood. To cut emissions, EPA suggests moderate temperatures, dehumidifying, and extra ventilation after new furniture or cabinets arrive. EPA also notes that table-top air cleaners may not remove enough pollution from strong nearby sources; if you buy one, size it by its CADR (clean air delivery rate).

What a CO2 monitor can tell you

CO2 comes from people's breath, so a reading shows how much fresh air reaches them: when outdoor air drops, CO2 rises along with other indoor-generated pollutants. ASHRAE explains that 1,000 ppm corresponds to about 8 liters per second (16 cfm) of outdoor air per person, a figure tied to body-odor complaints, not health. Outdoor air itself reached 426 ppm in 2024.

A CO2 monitor doesn't detect carbon monoxide or radon, and pollutants from building materials or outdoors don't track CO2. ASHRAE calls the evidence that typical indoor CO2 directly harms health, sleep or thinking inconsistent. OSHA's 5,000 ppm limit is for 8-hour workdays, not homes.

Sensor accuracy, placement and calibration matter, so read the trend: a bedroom that climbs steadily overnight with the door shut needs more airflow.

Frequently asked questions

Does a newly built or radon-resistant home still need a radon test?

Yes. EPA says every new home should be tested after move-in, even one built radon-resistant. At 4 pCi/L or more, a qualified mitigator can add a vent fan to make the passive system active.

Should I retest after a radon system is installed?

Yes: after the fix, then every two years, says EPA. Most systems have a monitor showing they're running. Retest if you start using a lower level, such as a basement.

Does a recirculating range hood count as ventilation?

Not under ASHRAE 62.2 or California's code, because it returns air to the kitchen. GAO notes the International Residential Code allows recirculating hoods alongside other ventilation, so rules elsewhere vary.

How often should a CO alarm be replaced?

The CDC says to follow the manufacturer's instructions, or replace it every five years. NFPA recommends an alarm carrying the label of a recognized testing laboratory. If you can't find the alarm's date, treat it as due.

If I switch to an electric or induction stove, do I still need a hood?

Yes, for different pollutants. Induction emitted no detectable benzene in the 2023 study, but GAO notes any stove releases fine particles during cooking such as pan frying. California requires vented hoods over electric ranges in new homes too.

A weekend indoor-air checklist

Order a radon kit and place it on the lowest lived-in level. At 4 pCi/L or more, follow up, then get mitigator bids if confirmed.
Test every CO alarm, confirm one per level and outside sleeping areas, and check replacement dates.
Book annual service for fuel-burning appliances.
Check that your hood vents outside (a duct or exterior vent cap), and use it every time you cook.
Put a hygrometer in a bedroom or basement and aim for 30% to 50%; call a professional for mold over about 10 sq ft.
Renters: send requests and test results to the landlord in writing, and keep a copy.