5 Danger Levels of Indoor Air Quality

When it comes to assessing a family’s indoor living environment, the Environmental Protection Agency (EPA) has identified five indoor air quality categories of concern that every homeowner should understand.

These are known as the five danger levels of indoor air quality.

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Indoor air quality is a major human health issue in both the United States and Canada. Studies show that people now spend up to 90% of their time indoors, especially as homes become more energy-efficient and tightly sealed.

While this improves energy savings, it can also make it harder for fresh, clean air to circulate.

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👉 Learn more about how indoor air quality affects your home and your family.

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In fact, there are approximately 750,000 new asthma cases each year in the U.S. alone, highlighting the growing importance of healthy indoor air.

So what exactly should homeowners be concerned about?

Let’s break down the five danger levels of indoor air quality and explain what they mean for your home and your family.

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Danger Level 5: Safety Gases

The most dangerous indoor air contaminants are radon and carbon monoxide.

They are classified as Level 5 because they can be fatal.

• Odorless
• Tasteless
• Invisible
• Extremely dangerous at high levels

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Radon

Radon is a naturally occurring radioactive gas released from the soil.

It is an off-gas of uranium found in the ground and can enter homes without warning.

• Responsible for 21,000 deaths per year in the U.S.
• Causes approximately 15% of all lung cancer fatalities

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Carbon Monoxide

Carbon monoxide exposure at low levels can cause symptoms that are often mistaken for the flu, such as:

• Headaches
• Dizziness
• Nausea
• Fatigue
• Disorientation

High levels of carbon monoxide exposure can be deadly.

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Danger Level 4: Microbial Growth

Microbial growth includes mold, mildew, fungal spores, and other microorganisms.

While mold exists naturally everywhere, it becomes a problem when it grows in areas it shouldn’t.

This is especially common in basements, crawl spaces, and other poorly ventilated areas.

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Common causes of elevated mold levels include:

• Inadequate ventilation
• Moisture intrusion
• Damp, stagnant air

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Potential health impacts include:

• Aggravated allergies
• Sinus and respiratory infections
• Severe long-term health effects in extreme cases

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Danger Level 3: Allergens and Particulates

Allergens and particulates are microscopic contaminants that circulate through your home’s air.

These include:

• Dust
• Pet dander
• Pollen
• Insect debris
• Smoke

They often travel through air ducts and rise through the home due to the stack effect.

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High levels may cause:

• Sneezing or coughing
• Congestion
• Nose and throat irritation
• Asthma flare-ups

Keeping your home dry, well-ventilated, and properly filtered can significantly reduce these issues.

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Danger Level 2: Infectious Illness

This category includes airborne illnesses such as colds, flu viruses, bacteria, and germs.

These microorganisms are commonly brought indoors by people or pets.

Once inside, they can circulate through the home’s air distribution system, increasing the spread of illness among occupants.

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This is why sickness spreads easily in shared environments like homes, offices, schools, and public transportation.

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Danger Level 1: Toxic Compounds

Toxic compounds can originate from both inside and outside the home.

Common sources include:

• Building materials
• Furniture and carpets
• Paints and cleaning products
• Pesticides and herbicides
• Natural gases such as methane

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Because modern homes are built tighter than ever, these toxins can become trapped indoors.

This is one reason childhood asthma rates have increased over 600% in the past 30 years.

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Improve Your Indoor Air Quality with TerraFirma

If you are concerned about any of the five danger levels of indoor air quality, it’s important to take action.

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Contact TerraFirma, your basement and crawl space experts, to evaluate your indoor air quality and identify effective solutions to help protect your home and your family.

TerraFirma has the experience, training, and tools needed to create a healthier indoor environment—starting from the ground up.