Top Causes of Poor Indoor Air Quality: VOCs, Mold & More

What Causes Poor Indoor Air Quality?

Poor indoor air quality is commonly caused by pollutants released inside a building, combined with inadequate ventilation. Frequent sources include volatile organic compounds, or VOCs; excess moisture and mold; combustion appliances; smoke; dust and allergens; radon; asbestos; pesticides; and outdoor pollution that enters the building.

The U.S. Environmental Protection Agency reports that concentrations of many VOCs can be up to 10 times higher indoors than outdoors. Studies of several common organic pollutants have found levels that were typically two to five times higher inside homes.

What Are the Most Common Causes of Poor Indoor Air Quality?

1. Volatile Organic Compounds, or VOCs

VOCs are chemicals that are released as gases from certain solids and liquids. Thousands of household, workplace, personal-care, construction, and maintenance products can release VOCs while they are being used—and sometimes while they are stored.

Common sources of VOCs include:

• Paint, varnish, paint stripper, and solvents
• New carpeting, flooring, and upholstery
• Composite or pressed-wood furniture and cabinets
• Cleaning products and disinfectants
• Air fresheners and scented candles
• Adhesives, glue, caulk, and sealants
• Cosmetics and personal-care products
• Aerosol sprays
• Copiers and printers
• Dry-cleaned clothing
• Moth repellents
• Pesticides
• Stored fuels and automotive products
• Hobby and craft supplies

VOC levels may rise during painting, cleaning, remodeling, installing new furniture or flooring, or using heavily scented products. Concentrations can remain elevated after the activity has ended.

2. Excess Moisture and Mold

Mold can grow when building materials remain damp because of leaks, flooding, condensation, high humidity, roof damage, plumbing problems, or inadequate ventilation.

Mold spores are naturally present indoors and outdoors. The key to controlling indoor mold growth is controlling moisture. Cleaning visible mold without correcting the underlying water or humidity problem may allow it to return.

Mold exposure may cause or aggravate:

• Stuffy or runny nose
• Sneezing
• Coughing or wheezing
• Sore throat
• Red, itchy, or watery eyes
• Skin irritation
• Asthma symptoms in susceptible individuals
• Reactions vary by person, and not everyone exposed to mold will experience symptoms.

3. Inadequate Ventilation

Poor ventilation allows pollutants to accumulate instead of being diluted with outdoor air or removed from the building.

Ventilation problems may be more noticeable in tightly sealed homes, offices, basements, bathrooms, kitchens, recently renovated spaces, and buildings with poorly maintained heating or cooling systems. High temperatures and humidity can also increase the concentration of certain indoor pollutants.

4. Fuel-Burning Appliances and Combustion Pollutants

Furnaces, boilers, fireplaces, wood-burning stoves, gas ranges, water heaters, space heaters, and other fuel-burning appliances can release pollutants when they are improperly installed, maintained, or vented.

Combustion pollutants may include:

• Carbon monoxide
• Nitrogen dioxide
• Smoke
• Soot
• Fine particulate matter
• Sulfur dioxide
• Blocked chimneys, damaged flues, leaking furnaces, improperly vented appliances, and exhaust from attached garages may contribute to indoor air problems.
• Carbon monoxide can be life-threatening and cannot be identified through odor alone. Homes should have properly installed and maintained carbon monoxide alarms.

5. Dust, Allergens, and Particulate Matter

Small airborne particles can come from cooking, fireplaces, candles, tobacco smoke, construction, deteriorating materials, outdoor pollution, and everyday dust.

Indoor dust may also contain:

• Pet dander
• Pollen
• Dust-mite allergens
• Mold fragments
• Fibers
• Pest debris
• Combustion residue
• Particles from building materials

Because different pollutants may be present in the same dust, identifying its composition can be useful when unexplained residue or recurring symptoms are a concern.

6. Radon

Radon is a naturally occurring radioactive gas that can enter buildings through cracks and openings in foundations, floors, and walls.

You cannot see or smell radon. Testing is the only way to determine whether a home, school, or workplace has an elevated radon level. The EPA recommends that all homes be tested.

7. Asbestos and Deteriorating Building Materials

Asbestos may be present in insulation, floor tile, pipe coverings, roofing, textured coatings, and other materials used in older buildings.

Asbestos-containing materials generally pose the greatest concern when they are damaged, deteriorating, or disturbed during renovation or demolition. Suspected materials should not be cut, sanded, scraped, drilled, or sampled without appropriate professional guidance.

What Are the Symptoms of Poor Indoor Air Quality?

Possible symptoms associated with exposure to certain indoor air pollutants include:

• Eye, nose, or throat irritation
• Headaches
• Dizziness
• Fatigue
• Nausea
• Persistent coughing
• Shortness of breath
• Difficulty concentrating
• Allergy-like symptoms
• Worsening asthma symptoms
• Skin irritation

These symptoms can have many possible causes and do not confirm that an indoor pollutant is present. However, an environmental cause may be worth investigating when symptoms:

• Began after moving, renovating, painting, or installing new furnishings
• Occur primarily in one building or room
• Improve after leaving the property
• Affect several occupants at the same time
• Appear alongside musty, chemical, smoky, or unusual odors
• Follow a leak, flood, fire, or other building-related event
• The EPA notes that symptoms associated with indoor pollution can resemble those of colds and other illnesses. Paying attention to when and where symptoms occur may help identify a possible environmental pattern.

Persistent or serious symptoms should be discussed with a qualified healthcare professional. Environmental testing does not replace medical diagnosis or treatment.

When Should You Test Your Indoor Air Quality?

Consider a professional indoor air quality assessment when:

• You notice persistent or unexplained odors
• Symptoms improve when you leave the building
• Several occupants experience similar symptoms
• There has been water damage, flooding, or a recurring leak
• You suspect hidden mold
• You recently painted, renovated, or installed new flooring or furniture
• You are concerned about VOC exposure
• There has been a fire, smoke event, or soot contamination
• You are buying or renovating an older property
• You need to identify an unknown dust or residue
• You want to test for radon or another pollutant that cannot be detected by sight or smell

What Does an Indoor Air Quality Assessment Include?

An indoor air quality investigation should be tailored to the building and the specific concern. Depending on the circumstances, an assessment may include:

• A visual inspection of the property
• Review of recent leaks, renovations, odors, or occupant concerns
• Evaluation of moisture or possible mold conditions
• Targeted air or surface sampling when appropriate
• VOC analysis
• Radon testing
• Allergen or particulate testing
• Identification of possible pollutant sources
• A written report explaining the findings and recommended next steps

RTK Environmental provides independent environmental testing and consulting and does not perform remediation. This separation helps property owners receive an unbiased assessment without a financial interest in the cleanup work.

Schedule Indoor Air Quality Testing

You cannot always see or smell the pollutants affecting a home or workplace. Professional testing can help determine whether VOCs, mold, radon, allergens, or other environmental conditions may be contributing to an indoor air concern.

Call RTK Environmental at 800.392.6468 to discuss your concerns or schedule an indoor air quality assessment.

Frequently Asked Questions

Can indoor air be more polluted than outdoor air?

Yes. Indoor pollutant levels can become elevated when chemicals, particles, moisture, or combustion byproducts are released inside a building and are not adequately removed through ventilation. The EPA reports that many VOC concentrations are consistently higher indoors than outdoors.

What is usually responsible for poor indoor air quality?

There is no single cause in every building. Common contributors include VOC-emitting products, excess moisture and mold, inadequate ventilation, combustion appliances, smoke, dust, allergens, radon, pesticides, asbestos-containing materials, and outdoor pollution.

Can new furniture or carpeting affect indoor air quality?

Some new furniture, cabinetry, carpeting, flooring, adhesives, and finishes can release VOCs through a process commonly called off-gassing. The type and amount of emissions depend on the materials, manufacturing process, age, temperature, humidity, and ventilation.

Can mold grow even when I cannot see it?

Yes. Mold may develop behind walls, beneath flooring, around plumbing, inside cabinets, near HVAC equipment, or in other areas affected by moisture. A musty odor, water staining, recurring humidity, or a past leak may indicate that further investigation is warranted.

How do I know whether my symptoms are caused by my building?

Symptoms alone cannot identify a specific pollutant. A potential environmental connection may be present when symptoms consistently appear in one location and improve after leaving. A healthcare professional can evaluate your symptoms, while an environmental inspector can investigate possible conditions in the building.

Can a home air quality monitor replace professional testing?

Consumer monitors can provide useful general information, but many do not identify individual VOCs, mold species, radon, asbestos, allergens, or the source of a problem. Additionally, consumer monitors fall out of calibration over time leading to inaccurate measurements. Professional testing may be needed when specific contaminants or building conditions must be identified.