Clean Indoor Air

Practical, evidence-based steps for the air you breathe at home

Last reviewed: October 2026 · 13 sources

Educational only, not medical advice. This page shares general information and community experience. It isn’t a diagnosis or a treatment plan. Please talk with your doctor or another licensed healthcare provider before starting, stopping, or changing any test, supplement, medication, or treatment.

At a glance

  • Three strategies: the EPA lists source control, better ventilation and air cleaners or filtration as the basic ways to improve indoor air [1].
  • Start with sources: removing or reducing pollution sources is usually the most effective step [1].
  • Control moisture: the EPA says “the key to mold control is moisture control” and suggests keeping indoor humidity below 60%, ideally 30–50% [2].
  • Filtration helps as a supplement: a portable air cleaner with a HEPA filter and a CADR sized for the room can reduce particles [3].
  • Avoid ozone: the EPA advises avoiding air cleaners that intentionally produce ozone, a lung irritant [3].

If you live with mold illness, MCAS or chemical sensitivity, you may already pay close attention to your home’s air. Whatever your situation, cleaner indoor air is a reasonable goal, and the most effective steps don’t require expensive gadgets [1]. Our family’s own recovery included better air filtration; you can read about it in our story. This guide sticks to what the evidence supports.

Why indoor air matters

Indoor air pollutants come from outdoors and from indoor sources and activities such as cooking, cleaning, secondhand smoke, building materials, consumer products and furnishings [3]. They can be particles or gases, including volatile organic compounds (VOCs) [3]. Concentrations of many VOCs are consistently higher indoors, up to ten times higher, than outdoors [4].

Step 1: Source control

The EPA says the most effective way to improve indoor air is usually to eliminate individual sources of pollution or reduce their emissions [1]. It is also more cost-efficient than increasing ventilation, which can raise energy costs [1].

  • Household products: VOC sources include paints and solvents, aerosol sprays, cleansers and disinfectants, air fresheners, stored fuels, hobby supplies and dry-cleaned clothing [4].
  • Use and storage: ventilate when using products that emit VOCs and follow label precautions [4]. ISEAI suggests storing paints, adhesives, solvents and pesticides away from living space and away from the air handler [5].
  • Fragrance: ISEAI suggests fragrance-free or unscented cleaning products, noting that “clean” isn’t defined by a smell [5]. Fragranced products are commonly reported triggers for people with chemical sensitivity [6]; see our chemical sensitivity guide.
  • Combustion: gas- and oil-burning furnaces, portable generators and charcoal grills produce carbon monoxide, an odorless, colorless gas [7]. The CDC advises battery-operated or battery back-up CO detectors near every sleeping area [7].

Step 2: Humidity and mold

Moisture control is the foundation of mold control [2].

  • Dry fast: drying water-damaged areas and items within 24–48 hours usually prevents mold growth [2].
  • Keep humidity in range: below 60%, ideally 30–50% [2]. An inexpensive humidity meter from a hardware store can measure it [2].
  • Reduce moisture at the source: vent clothes dryers and stoves outside where possible, use air conditioners or dehumidifiers when needed, and run the bathroom fan or open a window when showering [2].
  • Fix the cause: if mold is a problem, clean it up promptly and fix the water problem [2]. See our mold remediation decision tree and mold toxicity guide.

Step 3: Ventilation

Another way to lower indoor pollutants is to bring in more outdoor air [1]. Most home heating and cooling systems don’t mechanically bring fresh air into the house [1].

  • Open windows and doors or use window or attic fans when the weather permits [1].
  • Bathroom and kitchen fans that exhaust outdoors remove pollutants directly from the room [1].
  • ISEAI suggests running the range hood or opening a kitchen window while cooking, if outdoor air quality allows [5].

Step 4: Air cleaners and filters

The EPA says filtration can be an effective supplement to source control and ventilation, not a replacement [3]. Portable air cleaners and HVAC filters can reduce indoor air pollution, but they can’t remove all pollutants [8].

Choosing a portable air cleaner

  • Size it to the room. Choose a clean air delivery rate (CADR) large enough for the room [3]. The higher the CADR, the more particles it can filter [3].
  • HEPA for particles. Portable air cleaners often reach a high CADR by using a high-efficiency particulate air (HEPA) filter [3].
  • Gases need carbon. To filter gases, the EPA suggests an activated carbon filter [3]. There are no widely used performance ratings for gas removal; CADR covers particles only [3].
  • Run time. Higher fan speeds and longer run times increase the amount of air filtered [3].
  • HVAC filters. If you upgrade, the EPA suggests a filter rated at least MERV 13, or as high as your system can handle [3].

Ozone generators and “purifying” technologies

  • Ozone generators: the EPA says ozone can damage the lungs, and at levels that don’t exceed public health standards it does not effectively remove viruses, bacteria, mold or other biological pollutants [9].
  • Other electronic cleaners: air cleaners with electrostatic precipitators, ionizers, UV lights without adequate lamp coatings, and plasma technology may emit ozone in some cases [3]. An EPA technical summary reports that photocatalytic oxidation (PCO) cleaners have been shown to generate formaldehyde, acetaldehyde, nitrogen dioxide and carbon monoxide [10]. Evidence: EPA review of laboratory studies.
  • CARB certification: since 2010, portable indoor air cleaners sold in California must be certified by the California Air Resources Board [11]. Electronic air cleaners must meet an ozone emission limit of 0.050 parts per million [11]. CARB notes that certification doesn’t reflect effectiveness [11]. Its list of certified devices is a useful check for ozone [11].

VOCs, fragrance and the mold connection

VOCs include a variety of chemicals, some of which may have short- and long-term health effects [4]. For people sensitive to both mold and chemicals, the same habits help on both fronts: control moisture [2], choose low-VOC and fragrance-free products [5], and ventilate when using products that release VOCs [4]. The EPA does not recommend using a biocide such as chlorine bleach as a routine practice during mold cleanup [2].

Functional & integrative perspective · evidence varies

The functional and integrative perspective

ISEAI, a professional society focused on environmentally acquired illness, recommends many of the same basic steps as the EPA, with extra caution for sensitive people [5]. These are their views, described in their terms.

  • Physical filtration first. ISEAI suggests focusing on air cleaners that physically remove contaminants with a HEPA filter rather than those relying on “purification technologies” like UV, ionization, ozone or PCO, because it’s unsure whether those produce byproducts that could affect a sensitive person [5]. Evidence: consistent with EPA cautions.
  • The bedroom first. ISEAI suggests prioritizing bedroom air, using a HEPA unit there if possible [5]. Evidence: practical advice; not tested in trials.
  • Help with cleaning. ISEAI suggests sensitive people have someone else clean, wear an N95 mask during and after cleaning, and air out the home afterward [5]. Evidence: practical advice.
  • Be wary of marketing. ISEAI advises being wary of marketing claims, special technologies and high prices, and checking that “HEPA” isn’t used loosely [5]. Evidence: consumer caution.

This is not medical advice. Air cleaning supports a healthy home, but it isn’t a treatment for any condition.

What to do next

General information, not a diagnosis or a treatment plan. A licensed clinician can tell you which of these steps fit you.

  1. Step 1Start this week

    • Walk through your home and list pollution sources: air fresheners, cleaning products, stored paints or solvents, and combustion appliances [4, 7].
    • Check humidity with an inexpensive meter; aim for below 60%, ideally 30–50% [2].
    • Install or test CO detectors near sleeping areas [7].

  2. Step 2Fix moisture and sources first

    • Dry leaks within 24–48 hours and fix the water problem [2].
    • Switch to fragrance-free and low-VOC products where you can [5].

  3. Step 3Ventilate

    • Use bathroom and kitchen exhaust fans and open windows when outdoor air allows [1].

  4. Step 4Then add filtration

    • Choose a HEPA portable air cleaner with a CADR sized for the room, and consider a MERV 13 HVAC filter if your system can handle it [3].
    • Skip devices that intentionally make ozone, and check the CARB list for electronic cleaners [3, 11]. Evidence: EPA and CARB guidance.

  5. Step 5If symptoms seem tied to your home

    • Note when symptoms improve or worsen at home or away, and bring notes to your doctor [12]. Our Doctor visit prep sheet has space for exposures.

  6. Step 6When to get urgent care

    • CO symptoms are often described as “flu-like,” and breathing in a lot of CO can make you pass out or kill you [7]. See When to get urgent help.

When to get urgent help

Carbon monoxide can make you pass out or kill you, and people who are sleeping can die from it before they have symptoms [7]. For an inhaled poison such as carbon monoxide, get the person into fresh air right away; if someone has passed out, call 911 or your local emergency number [13].

Sources

Numbers in brackets in the text link to these sources. Links were checked in October 2026. Some sources are written by people who support a particular approach; we've tried to say so in the text.

  1. EPA. Improving Indoor Air Quality. Web page, accessed October 18, 2026. https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality
  2. EPA. A Brief Guide to Mold, Moisture and Your Home. Web page, accessed October 18, 2026. https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home
  3. EPA. Guide to Air Cleaners in the Home. Web page, accessed October 18, 2026. https://www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home
  4. EPA. Volatile Organic Compounds’ Impact on Indoor Air Quality. Web page, accessed October 18, 2026. https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality
  5. International Society for Environmentally Acquired Illness (ISEAI). Clean Indoor Air on a Budget – Helpful Tips for Chronically Ill Patients. June 29, 2023. Web page, accessed October 18, 2026. https://iseai.org/clean-indoor-air-on-a-budget/
  6. RincĂłn R, Perales R, Palmer RF, et al. Environmental house calls can reduce symptoms of chemical intolerance: a demonstration of personalized exposure medicine. Prim Health Care Res Dev. 2024;25:e53. PMID: 39434594. https://pmc.ncbi.nlm.nih.gov/articles/PMC11569860/
  7. CDC. Carbon Monoxide Poisoning Basics. Web page, accessed October 18, 2026. https://www.cdc.gov/carbon-monoxide/about/index.html
  8. EPA. Air Cleaners and Air Filters in the Home. Web page, accessed October 18, 2026. https://www.epa.gov/indoor-air-quality-iaq/air-cleaners-and-air-filters-home
  9. EPA. Ozone Generators that are Sold as Air Cleaners. Web page, accessed October 18, 2026. https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners
  10. EPA. Residential Air Cleaners: A Technical Summary, 3rd edition (EPA 402-F-09-002). July 2018. https://www.epa.gov/sites/default/files/2018-07/documents/residential_air_cleaners_-_a_technical_summary_3rd_edition.pdf
  11. California Air Resources Board (CARB). List of CARB-Certified Air Cleaning Devices. Web page, accessed October 18, 2026. https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-products/california-certified-air-cleaning-devices
  12. National Institute on Aging (NIA). What Do I Need to Tell the Doctor? Accessed October 17, 2026. https://www.nia.nih.gov/health/medical-care-and-appointments/what-do-i-need-tell-doctor
  13. MedlinePlus Medical Encyclopedia. Poisoning. Web page, accessed October 18, 2026. https://medlineplus.gov/ency/patientinstructions/000718.htm

Products our family uses

Personal picks, separate from the cited guide above. Some links earn us a small commission at no extra cost to you. About affiliate links

Air Oasis

Purifiers combining H13 HEPA and carbon filtration with UV-C and bipolar ionization. We like having a simple option to share with anyone working on the air in their home.

Its current iAdaptAir 2.0 models are on California’s list of certified air cleaners, tested to stay under the state’s ozone limit; CARB notes that certification doesn’t reflect effectiveness.

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Branch Basics

Fragrance-free, non-toxic cleaning products. We like that they keep cleaning simple and scent-free.

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Whatever air cleaner you consider, the guide’s sections on choosing a portable air cleaner and “purifying” technologies explain what the EPA suggests.

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