How Safe Is the Air Inside Your Home or Workplace?

What the research says about indoor air pollution, sick building syndrome, radon, and mold — and how to know when to test.

Indoor air pollution can cause symptoms like allergies, headaches, fatigue, and cold- or flu-like symptoms. Below, we break down the data behind these risks, what typically causes them, and when it’s time to test.

What Are the Signs Your Indoor Air May Be Unsafe?

The clearest sign of an indoor air quality problem is symptoms that appear indoors and ease once you leave. Common warning signs include:

• Allergy symptoms (sneezing, congestion, itchy eyes)
• Headaches
• Fatigue
• Cold- or flu-like symptoms with no clear illness

If these symptoms occur indoors and improve when you leave, indoor air pollution may be the cause — this pattern is the hallmark clinicians and industrial hygienists use to distinguish an environmental cause from an actual illness.

What Causes Poor Indoor Air Quality?

Two categories drive most residential and workplace indoor air quality complaints: volatile organic compounds (VOCs) and mold.

According to the EPA, concentrations of many VOCs are consistently higher indoors than outdoors — up to ten times higher — because they off-gas continuously from everyday products rather than dispersing the way outdoor pollutants do.

Source: EPA — Volatile Organic Compounds’ Impact on Indoor Air Quality

VOCs and toxic fumes are commonly found in:

• Paints and solvents
• Cleansers and disinfectants
• Carpets and air fresheners
• Pesticides and glue
• Home furnishings and building materials

These pollutants build up indoors, especially in tightly sealed, energy-efficient homes with limited air exchange — a trade-off the EPA has flagged as a growing contributor to indoor pollutant concentrations.

Source: EPA — Indoor Air Quality (Report on the Environment)

Indoor vs. Outdoor Air Pollution: The Data

What Is Sick Building Syndrome?

Sick Building Syndrome (SBS) describes a pattern where occupants feel unwell while inside a specific building — home, office, or apartment — but improve shortly after leaving. It’s a recognized environmental health phenomenon, not a single diagnosis, and it’s driven by the building’s air quality rather than an underlying illness.

Research suggests roughly 1 in 5 building occupants report SBS-type symptoms tied to their workplace or home, though prevalence varies widely by building type — hospital studies alone have found rates ranging from about 21% to over 80% depending on ventilation and environmental conditions.

Source: PMC — Sick Building Syndrome and Other Building-Related Illnesses

If symptoms only occur in a specific location, such as your home, office, or apartment, this may indicate an indoor air quality issue worth investigating.

What Are the Symptoms of Sick Building Syndrome?

Common symptoms include:

• Typical seasonal-allergy symptoms
• Asthma
• Persistent cough
• General malaise
• Excessive fatigue
• Eye irritation
• Nose and throat irritation
• Headaches
• Loss of coordination
• Nausea

More serious, longer-term impacts of poor indoor air quality can include liver damage, kidney damage, and central nervous system damage. Children, older adults, and pets are most at risk, since they’re more physiologically vulnerable to airborne contaminants and often spend more time in the affected space.

Source: EPA — Indoor Air Pollution: An Introduction for Health Professionals

What Does Indoor Air Quality Testing Check For?

RTK Environmental’s Indoor Air Quality testing evaluates the pollutants most strongly linked to the health effects above:

• VOCs
• Mold
• Mycotoxins
• Carbon monoxide
• Radon
• Common allergens

Investigators identify the root cause of air quality issues and provide a clear, detailed report. After mitigation, follow-up testing confirms the issue has been resolved.

Why Is Radon Testing Important?

Radon is the second leading cause of lung cancer in the United States, responsible for an estimated 21,000 lung cancer deaths every year — and it’s the leading cause of lung cancer among people who have never smoked, according to the EPA and CDC.

Source: EPA — Health Risk of Radon

• It’s a naturally occurring radioactive gas
• It’s odorless, tasteless, and invisible
• It forms when uranium breaks down in soil, rock, and water

Radon risk depends heavily on local geology. The EPA’s Map of Radon Zones rates counties on a three-tier scale, and much of the Northeast — including large portions of New York, New Jersey, Pennsylvania, and Connecticut — falls into Zone 1, the EPA’s highest-potential category. But the agency is clear that elevated levels have been found in homes in all three zones, so zone alone can’t rule a home in or out. Testing is the only way to know your home’s actual level.

Source: EPA — The EPA Map of Radon Zones

The EPA recommends taking action if your home tests at 4 picocuries per liter (pCi/L) or higher, and considering mitigation between 2 and 4 pCi/L.

When Should You Test Your Indoor Air?

You should consider testing if:

• You experience unexplained symptoms indoors
• You notice odors or discomfort in a specific space
• You want to check for radon, mold, or VOCs
• You’re buying, selling, or renovating a home
• Your home or building has had past water damage or visible mold

Frequently Asked Questions

Is indoor air really more polluted than outdoor air?

Yes. The EPA estimates indoor air can be 2 to 5 times more polluted than outdoor air, and in some cases up to 100 times more polluted, largely due to VOCs and mold that accumulate in enclosed, poorly ventilated spaces.

What percentage of indoor air quality problems come from VOCs and mold?

VOCs and mold are consistently identified as the two leading contributors to residential and workplace IAQ complaints. Studies estimate that 18% to 50% of buildings have some degree of dampness or mold, and EPA data shows VOC concentrations can run up to 10 times higher indoors than outdoors.

Source: NIH/PMC — Dampness, Mold, and Respiratory Health

How common is Sick Building Syndrome?

Estimates vary by setting, but research commonly cites roughly 1 in 5 occupants reporting SBS-related symptoms, with some hospital and office studies finding rates as high as 80% in poorly ventilated buildings.

Why is radon dangerous if I can’t see or smell it?

Radon is a radioactive gas that damages lung tissue through inhaled radiation, not through smell or irritation — so there’s no physical warning sign. It causes an estimated 21,000 lung cancer deaths per year in the U.S., making testing the only way to know your exposure.

Source: EPA — Health Risk of Radon

How do I know if my symptoms are caused by my building’s air?

The strongest indicator is timing: symptoms that appear or worsen indoors and improve after you leave the building point toward an environmental cause rather than a separate illness. Professional IAQ testing can confirm the specific pollutant involved.

Explore More

• VOC Resource Guide
• Find out when to test your IAQ
• Learn about the RTK approach to Indoor Air Quality and Radon
• About our Commercial Indoor Air Quality and Radon testing
• Specialty Testing
• Dust Characterization
• Poor IAQ Symptoms