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How to Improve Indoor Air Quality

Derek Hales

Written By: Derek Hales

Updated on:

The risk of pollution exposure is inevitable in our everyday lives. From cars and planes to the paint we use on our walls, potential sources of contaminants can hide anywhere, and perhaps nowhere more than in the air we breathe.

How to Improve Indoor Air quality

Table of Contents

This guide is going to take a closer look at air pollution and discuss the following hot topics:

Indoor pollution is often worse than outdoors. An estimated 90 percent of the time is spent indoors in developed countries, so indoor air quality also has a greater health impact, especially in those countries and particularly on vulnerable populations such as children, the elderly, and anyone with existing respiratory or cardiovascular issues. 

Where does air pollution come from?

Air pollution comes from four main sources:

Mobile sources of air pollution

Mobile Sources

planes, cars, buses

Stationary sources of air pollution

Stationary Sources

power plants, oil refineries, industrial facilities, factories

area sources of air pollution

Area Sources

agricultural areas, cities, fireplaces

natural sources of air pollution (volcano)

Natural sources

wind, dust, wildfires, volcanoes

While contaminants emitted from manufacturing, mobile, and natural sources may be out of our immediate control, we CAN take steps to help minimize our exposure to indoor air pollution. 

Here we will look at indoor air quality—what it is, how it impacts our health, what causes problems with our air, and what we can do.

What is Indoor Air Quality?

Indoor Air Quality (IAQ) generally refers to the quality of air in and around buildings or structures, particularly as it relates to the health and comfort of the occupants.

IAQ is considered a primary part of Indoor Environmental Quality (IEQ), which includes other indoor conditions such as lighting, thermal conditions, and ergonomics as well as air quality. 

Indoor air quality factors

When addressing IAQ/IEQ issues, strategies usually fall into three categories:

  • Protecting human health
  • Improving quality of life
  • Reducing stress and risk of injury

In addition to improving the lives of building occupants, which is of course the primary concern, better indoor air quality can increase resale values and reduce liability issues.

The more you understand and actively reduce common pollutants in your environment, the more you can reduce your health and business risks. 

How does indoor air quality affect my health?

The health effects of changes in your IAQ (whether for better or worse) can be felt immediately or take years to be seen, depending on length, intensity, and frequency of exposure.

Air Quality Health Effects
indoor air quality can have a significant effect on ones health

Reactions to poor indoor air quality can also vary based on the age, health, and individual sensitivity, including increased sensitivity after cumulative, high, or repeated exposure. 

Common Immediate Symptoms

  • Eye, nose, and throat irritation
  • Headaches
  • Dizziness
  • Fatigue 
  • Difficulty concentrating
  • Nausea
  • Aggravation of existing symptoms like asthma or allergies

Immediate symptoms like these are usually temporary and treatable, often by simply eliminating the source. They can closely resemble a cold or flu, so if you’re unsure what may be triggering the symptoms, pay close attention to when and where the symptoms start.

Also consider tracking how they respond to changes in ventilation, temperature, or humidity. 

Common Longer Term Effects

After lengthy, repeated, or intense exposure, more serious symptoms can present as various diseases, such as:

  • Respiratory disease
  • Heart disease
  • Cancer 

Individual reactions and specific contaminants make it difficult to fully know what concentrations or periods of exposure create specific health issues. Your best course of action is reduce your health risk wherever possible. This means knowing what leads to IAQ degradation and what steps to take to improve your IAQ. 

What is considered good indoor air quality?

Good IAQ should include comfortable temperature and humidity, adequate supply of fresh outdoor air, and control of pollutants from inside and outside of the building.

Measuring Indoor Air Quality

No specific standards have been created for measuring IAQ, because so many different variables impact it in so many direct and indirect ways. For example, many products in the home will release various chemicals that evaporate at room temperature into the air as gases in a process known as “off-gassing”.

These Volatile Organic Compounds (VOCs) can be mildly or extremely toxic over short or long periods of time. 

Knowing the source is easier than measuring the risk VOCs pose. If looking at these off-gassed VOCs in the air, one commonly used guideline suggests, if measuring in milligrams per cubic meter of air (mg/m3):

  • Less than 0.3 mg/m3 = Low level of concern 
  • 0.3 to 0.5 mg/m3 = Acceptable level of concern
  • 0.5 to 1 mg/m3 = Marginal level of concern
  • 1 to 3 mg/m3 = High level of concern 

That is not an officially set standard, however, and measuring a home’s Total VOC (TVOC) is problematic. Handheld consumer devices can be inaccurate, and according the Indoor Air Quality Scientific Findings Resource Bank (part of the Lawrence Berkeley National Laboratory), even professional measurements can be unreliable since:

  1. Different measurement methods yield different results
  2. Different VOCs will be present in different concentrations, so the overall TVOC level is not really representative of total toxicity.

Difficulty of Measurement

This difficulty in measuring concentrations and assessing risk applies to most other indoor pollutants, both in homes and in workplaces.

While OSHA (Occupational Health and Safety Administration) does aim to provide healthy and safe workplaces by developing and enforcing standards, currently it has no set IAQ standards.

OSHA does, however, provide guidelines about the most common IAQ workplace complaints.

Thus, maintaining a healthy indoor air quality both at home and in the workplace really does revolve around maintaining the health and comfort of the occupants by ensuring temperature control, fresh ventilation, and internal/surrounding pollutant control.

What causes indoor air quality issues?

Indoor air quality can affect a person’s health, comfort, and ability to live and work. IAQ is impacted by factors such as:

  • Temperature
  • Humidity 
  • Ventilation 
  • Moisture and mold
  • Outdoor air quality
  • Chemicals that off-gas as Volatile Organic Compounds (VOCs)

Other activities in or near a building, such as remodeling, construction, or insect control, can affect the fresh air coming into the building by stirring up dust, releasing spores lying dormant in the dirt, or using chemicals.

Construction Stirring Up Pollutants
dust, spores, and other harmful particles can be released into the air by construction sites and affect nearby air quality

According to both the Environmental Protection Agency (EPA) and the Consumer Product Safety Commission (CPSC), indoor air quality problems come primarily from pollution/contaminants, ventilation issues, and high temperatures and humidity. 

Pollutants and IAQ

US Green Technology lists the seven most common indoor pollutants as:

  • Carbon monoxide 
  • Radon
  • Nitrogen Dioxide
  • Secondhand smoke
  • Lead 
  • Asbestos
  • Mold

Pollutants can also be biological, such as bacteria, viruses, animal dander and cat saliva, house dust, mites, cockroaches, and pollen.

Common sources of indoor air contaminants

  • Tobacco products used inside or near entrances
  • Building materials including paints, sealants, varnishes, and glues that off-gas toxic VOCs at room temperature 
  • Furnishings including old insulation containing asbestos, new flooring/upholstery/carpet, and pressed wood furniture made with adhesives or other toxic chemicals
  • Combustion and fuel-burning sources such as fireplaces, stoves, vehicles running in garage/near entrances, oil, gas, kerosene, and wood
  • Mold from excess moisture 
  • Heating, Ventilation, and Air Conditioning (HVAC) systems
  • Cleaning products and hobby supplies
  • Radon or methane emitted from soil beneath buildings
  • Outside sources such as pesticides and other outdoor pollution 
  • Germs and other pathogens brought inside by being tracked in on shoes or from human respiration 

The impact of each specific source depends on the quantity of its emission, its toxicity level, and how often it emits contaminants. Activity like smoking, cleaning, and using hobby/craft supplies usually release pollutants only when used or opened. Building materials and furnishings can emit almost continuously.

Maintenance matters too; an old badly adjusted gas stove will release much more carbon monoxide than one that is well-adjusted. 

More about specific indoor pollutants and their sources can be found in the indoor air quality section of the EPA website. 

Inadequate Ventilation Concerns

After pollutants, ventilation is the second major factor impacting IAQ. Too little outdoor air diluting the indoor air allows the airborne pollutants to build up to more dangerous levels.

While potentially decreasing energy costs, buildings that are designed to minimize air coming in or “leaking out” can have higher levels of airborne contaminants, unless special ventilation systems are also included in the architectural design. 

Building Ventilation Affects Air Quality

Ventilation is also considered inadequate if the nearby outside air being brought in is contaminated by construction, natural sources, or smoking near entrances. 

The rate at which outdoor air replaces indoor air is known as the air exchange rate. The goal for adequate ventilation is to create a good air exchange rate by moving the air in and out of buildings enough to dilute or carry away as many contaminants as possible, thereby decreasing pollutant levels.

Outdoor air enters and leaves a building through three processes:

  • Infiltration, as air seeps into and out of buildings through openings, cracks, and joints in and around ceilings, floors, windows, and doors. 
  • Natural Ventilation, from air moving through opened doors and windows.
  • Mechanical Ventilation, using either outdoor-vented fans for single rooms (e.g., bathroom fan) or air handling systems that use ducts and fans to move, remove, and redistribute filtered and conditioned air from outdoors through the indoor environment. 

When inadequate ventilation causes a low or contaminated air exchange rate, pollutant levels can increase.

Humidity, Temperature and IAQ

Excessive humidity and temperatures can increase the concentration levels, accelerate the release of certain contaminants, or cause dermal problems. 

Humidity

Indoor air humidity is a bit like Goldilocks—finding that “just right” spot can be tricky. 

According to the indoor air risk assessment written by the European Commission’s Scientific Committee on Health and Environment Risks, too low humidity results in increased skin symptoms (e.g., dryness, rash), eye irritation, and nasal dryness. 

Too high humidity can create water damage and mold problems as the water in the air condenses onto surfaces. High humidity also supports the proliferation of dust mites. 

Excessive moisture from high humidity (whether natural or from humidifiers) is usually more concerning as related to indoor air quality. High humidity can expose occupants not just to mold and mites but also to other biological contaminants such as other fungi, bacteria, infections, and even certain viruses. 

Sneezing From Mold and High Humidity
high indoor humidity can lead to the propagation of fungi, mold, and contaminants that contribute to allergy or illness

What about mold?

Mold is of particular concern, given its connection to conditions such as asthma, allergic reactions, lung infections, and hypersensitivity pneumonitis (lung inflammation from breathing in allergens which can lead to permanent pulmonary scarring). 

While most people don’t react to mold exposure in indoor or outdoor air, those with certain underlying conditions may be more susceptible to mold-related reactions, infections, or diseases. 

Special care should be taken for individuals who:

  • Have existing allergies, asthma, sinus problems, or other lung issues
  • Have weakened immune systems from diabetes, leukemia, AIDS, or other autoimmune disease
  • Pregnant
  • Recovering from surgery, especially if an organ or bone marrow transplant recipient
  • Receiving chemotherapy or long-term steroid treatment
  • Children or elderly

Common health effects related to mold exposure closely resemble pollen or animal allergies, including:

  • Sneezing
  • Runny nose
  • Eye irritation
  • Coughing
  • Congestion
  • Aggravation of asthma
  • Skin rash

If not sure what the symptoms may be related to, try tracking their onset to see when they start and when they seem to be most aggravated. Eliminating all indoor exposure to molds and mold spores is impossible. However, moisture control is the most important strategy for reducing indoor mold growth.

Temperature

Higher temperatures can impact the rate at which materials off-gas VOCs into the air. The  higher the temperature, the more VOCs increase the concentration of airborne contaminants. Extreme heat can also increase the potential of indoor moisture if not controlled.

Nest Smart Thermostat
Nest Smart Thermostat

Ventilation can help control both humidity and temperature impacts on IAQ as well as reducing chemical pollutants, so the interplay between these three elements is crucial to maintaining a healthy IAQ. 

How To Measure Indoor Air Quality

People often wonder, “Is there a test that can find an indoor air quality problem?”

Unfortunately, there is no one test to identify IAQ issues. Other than checking temperature, air flow and ventilation, and humidity, although you can take steps to identify and address problems (See “Identifying IAQ Problems” below)

Measuring Pollutant Levels

While no one test for IAQ exists, some measurements are possible and some you can initiate yourself, such as air cleaners or for radon.

A number of air quality measurement devices can reveal airborne particulate levels, AQI, VOCs, formaldehyde, and more. These devices, especially the less expensive versions, may not provide perfect data. However, they can help to reveal if you have critical air quality issues in your home, office, or other building.

Radon Dectectors
radon detectors found at your local hardware store

The federal government recommends that homeowners measure the level of radon in their homes. Inexpensive devices are available for measuring this colorless, odorless, radioactive gas. The EPA provides information about risks associated with different exposure levels and when corrective action should be considered to reduce levels of radon in the home.

Air Quality Testing meter
Electronic testing meter we use to measure particulates and air quality

Because testing for many pollutants can get pricey, measurements for other pollutants are most appropriate when you notice:

  • Health symptoms
  • Signs of poor ventilation
  • Specific sources of pollutants have been identified as possible causes of indoor air quality problems.

Before investing in substantial testing, consult your state or local health department or professionals who have experience in solving indoor air quality problems in non-industrial buildings.

Identifying Indoor Air Quality Problems

In the absence of specific ways to measure or test indoor air quality, check for other indicators if you think you might have an IAQ problem.

#1. Be aware of new physical symptoms.

Track any symptoms related to health effects listed earlier. They can indicate possible IAQ issues, especially if they appear upon moving to a new building, remodeling or redecorating, or using new outdoor chemicals like pesticides, paints, or fuel.

Where is lead paint found?

Discuss any potential issues with your healthcare provider, local health department, or allergist. 

#2. Identify potential sources of indoor air pollution.

Check for common sources of indoor air contaminants as listed in the section above. Having any of the present in your home does not necessarily mean IAQ issues, but you may find just knowing potential sources helpful in determining any issues.

#3. Look at your lifestyle and activities.

Smoking, using craft and hobby supplies, remodeling—Human activities can be significant sources of indoor air pollution especially if involving VOC-releasing materials. 

Smoking Indoors

If you’re looking to smoke indoors without it smelling it and reduce its indoor air pollution, we wrote this article just for you.

#4. Look for signs of problems with the ventilation in your home.

Low or inadequate ventilation can show in moisture condensation on windows or walls, smelly or stuffy air, dirty central heating and air cooling equipment, and moldy books, shoes, or other items. People become “nose-blind” so try stepping outside for a few minutes then noticing what odors are noticeable upon re-entry. 

#5. Check the physical structure of your home. 

Water damage, leaks, dirt or pest droppings are all indicators of potential sources of IAQ contamination. 

How to improve indoor air quality?

The three best strategies for improving Internal Air Quality are Source Control, Ventilation Improvements, and Air Cleaners, according to the U.S. Consumer Product Safety Commission.

#1. Control the Source

Eliminating pollution sources or reducing their emissions is usually the most efficient and cost-effective way to improve IAQ and reduce exposure. Enclose or seal anything that may contain asbestos.

Gas appliances can be adjusted to decrease the number of emissions. Eliminate leaks and standing water in humidifiers, air conditioning units, on roofs, and in boiler pans that can become contaminated with bacteria or fungi. 

If considering remodeling:

  • Choose building materials and furnishings that will keep indoor air pollution to a minimum.
  • Use exterior-grade pressed wood products or solid wood products to avoid the formaldehyde and other VOCs in pressed wood. 
  • Install an effective moisture barrier prior to installing carpet if it is going to contact the ground, like in a basement. 
  • Do not permanently adhere carpet to concrete with adhesives so that the carpet can be removed if it becomes wet.
  • Ensure proper drainage and foundation seals. 
  • Make sure combustion appliances, including furnaces, fireplaces, wood stoves, and heaters, are properly vented and receive enough supply air.

Specific sources of indoor air pollutants, their impacts, ways to detect, and potential steps to control them can be further researched with the USCPC, the EPA, and in this Modern Castle article.

#2. Ventilation Improvements

Increasing ventilation can increase energy costs but is just as important. Increase the amount of outdoor air circulating with indoor air. Most mechanical ventilation systems don’t automatically bring in outside air.

So opening windows and doors, running fans, or using window air conditioners with the vent control open creates a better airflow exchange rate. 

Pay particular attention to these steps when engaged in temporary activities that can generate high levels of pollutants–painting, paint stripping, heating with kerosene heaters, cooking, or engaging in maintenance and hobby activities such as welding, soldering, or sanding. Try doing these activities outdoors when possible. 

#3. Air Purifiers & Air Cleaners

Use an air purifier. Options range from small area models to large whole-house systems. Their effectiveness varies based on their particle removal rate and how powerful the pollutant source may be.

Digital display screen on the Hathaspace air purifier
Digital display screen on the Hathaspace air purifier

Look for a model that has both a high particle collection rate (percentage efficiency rate) as well as a good airflow rate through its filtering elements (cubic feet per minute).

You can find a full list of our air purifier reviews here. Also, here are some of the best air purifiers we’ve tested..

Small models may only be effective if used simultaneously with attempts to remove the source itself. Remember that they are not usually designed to remove gaseous pollutants including radon.

Levoit H133 air purifier review
Levoit H133 air purifier

Maintain any model you use according to the manufacturer’s specifications for maximum effectiveness.

EPA’s booklet, Guide to Air Cleaners in the Home provides further information on air-cleaning devices to reduce indoor air pollutants.

Final Thoughts

Indoor Air Quality contributes to your health and well-being in countless ways. While it may seem overwhelming, you have many options of steps to take and resources to consult.

  • Watch for indoor pollution sources that can release gases or particles into the air.
  • Remember that poor ventilation exacerbates the problem by not providing enough clean air from outside to dilute the indoor emissions, or by bringing in already contaminated air. 
  • Check your indoor temperature and humidity. Knowing signs in the house and symptoms to look for will allow you to identify and address small problems before they grow out of control. 

Educating yourself on and reducing your indoor contaminant risk will protect not just your health, but your home as well. 

About Derek Hales

Derek HalesDerek Hales is the Founder and Editor-in-Chief of ModernCastle.com. He has been featured in Fast Company, Reader's Digest, Business Insider, Realtor.com, She Knows, and other major publications. Derek has a Bachelor's Degree in Business Administration from Kansas State University. Hales has been testing and reviewing products for the home since 2014.