Most of us exercise to strengthen our bodies and minds, yet the air we breathe during a workout is often overlooked.
Air quality can significantly affect both exercise performance and overall health, particularly during high-intensity or prolonged workouts. As breathing rate increases, exposure to airborne pollutants increases along with it. In enclosed spaces like gyms and studios, poor ventilation can allow pollutants to build up, potentially undermining the benefits of physical activity.
With the right awareness and a few practical adjustments, it’s possible to protect your lungs and get more out of every workout. Here’s how air quality affects exercise—and what to do about it.
How air quality impacts your workout
When you exercise, your breathing deepens and quickens. While this flood of oxygen fuels your muscles, it also means you’re inhaling more of whatever else is in the air: dust, mold, volatile organic compounds (VOCs) from cleaning products, and even PM2.5 —tiny particulate matter measuring less than 2.5 microns in diameter—can enter your lungs and circulate throughout the body. Studies confirm that indoor air pollution levels in gyms often surpass WHO safety limits (1).
During a high-intensity workout, you might inhale 90 liters of air per minute or more, compared to just 6 liters at rest (2). That’s 18 times more pollutants entering your lungs and bloodstream—where they can trigger inflammation and limit oxygen delivery to working muscles.
Both PM2.5 and gases like carbon dioxide (CO2) accumulate quickly in enclosed spaces. These irritants inflame airways, making it harder to breathe deeply and efficiently. Over time, this can lead to chronic oxidative stress, weakening lung function and endurance.
A 2018 study found that gyms in Brazil, France, and other areas of Europe had CO2 levels exceeding 1,000 ppm, a threshold linked to cognitive decline and fatigue (3). Poor ventilation was the primary contributor. Indoor air can harbor two to five times more pollutants than outdoor air, according to the U.S. EPA (4).
Why indoor air quality matters during exercise
It’s easy to assume that indoor workout spaces are inherently cleaner than the air outdoors. In reality, indoor air quality can vary widely depending on ventilation, occupancy, and cleaning practices.
During exercise, deeper and faster breathing increases exposure to airborne pollutants—even when they’re present at levels that might go unnoticed at rest. A gym that looks clean or smells fresh may still contain elevated levels of particulate matter or carbon dioxide, particularly during busy classes or peak hours.
This doesn’t mean indoor exercise is unsafe—it means air quality plays a larger role in workouts than many people realize, and that managing ventilation and filtration can make a meaningful difference.
Health risks of exercising in polluted air
The effects of poor air quality are measurable, both immediately and over time.
- Fatigue and reduced performance: Exposure to PM2.5 has been found to increase fatigue, affecting athletic performance (5).
- Respiratory issues: Regular exposure to air pollutants is linked to asthma-like symptoms and decreased lung capacity, even in healthy individuals, due to increased respiratory demands (6).
- Cardiovascular risks: A systematic review of studies focused on endurance exercise and air pollution shows that athletes exposed to elevated PM2.5 levels were significantly impacted with cardiovascular health problems (7).
- Mental health impacts: Chronic inflammation from poor air quality is associated with increased risk of depression and anxiety, undermining the mood-boosting effects of physical activity (8).
When to adjust your workout for air quality
Air quality doesn’t have to be “Hazardous” to affect exercise performance. Because breathing rates increase during physical activity, even moderate pollution can have a greater impact during intense or prolonged workouts. The key is knowing whether you’re responding to indoor air conditions or outdoor pollution levels—and adjusting accordingly.
Indoors: watch ventilation and buildup
For indoor workouts, elevated PM2.5 levels or carbon dioxide (CO₂) concentrations above 1,000 parts per million (ppm) can signal that ventilation may be inadequate—especially in crowded or enclosed spaces.
When these levels rise, lowering workout intensity, shortening duration, improving ventilation, or choosing a less crowded space can help reduce unnecessary strain on the lungs and cardiovascular system.
Outdoors: use air quality ranges to guide decisions
For outdoor exercise, PM2.5 and overall air quality levels are more useful decision tools.
As a general guide:
- Good (0–25): Air quality is good. Outdoor exercise is generally safe.
- Moderate (26–50): Air quality is acceptable, but sensitive individuals may notice symptoms during outdoor exercise.
- Moderately Unhealthy (51–100): Pollutants may affect breathing even in healthy individuals. Consider exercising indoors or keeping outdoor workouts shorter and less intense.
- Unhealthy for Sensitive Groups (101–150): Everyone may be affected, especially those with heart or lung conditions. Indoor exercise is the safer choice.
- Very Unhealthy (151–200): Health effects are more likely for everyone. Avoid outdoor exercise.
- Hazardous (201–500): Air quality is poor enough to pose serious health risks. Stay indoors and avoid physical exertion.
Using these ranges helps shift workouts to safer times, locations, or environments—without avoiding exercise altogether.
Using air quality data to plan your workouts
Air quality can change quickly due to traffic patterns, weather, and human activity. Pollution levels that are low early in the day may rise within hours, particularly during rush hour or in enclosed indoor spaces with high occupancy.
Checking real-time air quality data and short-term forecasts helps you decide when and where to exercise with less exposure.
Monitoring pollutants like PM2.5 and carbon dioxide allows you to adjust workout timing, intensity, or location accordingly—such as exercising earlier, choosing a less crowded space, or prioritizing indoor workouts when outdoor air quality is poor.
Indoor vs. Outdoor Exercise: Which Is Better?
When air quality is poor, the choice between exercising indoors or outdoors isn’t always straightforward. Outdoor workouts may offer better airflow, but they also expose you directly to pollution from traffic, industry, wildfire smoke, and other airborne contaminants.
Indoor exercise can reduce exposure when ventilation and filtration are adequate, but poorly ventilated gyms or studios can allow pollutants like PM2.5 to accumulate—especially during busy classes or peak hours.
In general, the better option depends on conditions:
- When outdoor air quality is good, exercising outside or ventilating indoor spaces can be beneficial.
- When outdoor air quality is poor, well-filtered and properly ventilated indoor environments are often the safer choice.
Monitoring air quality both indoors and outdoors helps you choose the option that minimizes exposure while still supporting your fitness goals.
How to exercise safely indoors
Indoor exercise can be made safer with a few practical adjustments. Paying attention to ventilation, filtration, and air quality helps reduce unnecessary exposure during workouts.
Choosing a gym or fitness studio:
- Prioritize facilities with high performance air purifiers.
- Ask staff about their ventilation systems and cleaning protocols. Gyms using green-certified products and frequent air exchanges are safer bets.
- Consider outdoor workouts when possible, if the air quality is good. Parks or open-air studios provide better airflow than indoor studios.
- Download a free air quality app to know what the air is like before you go outdoors to exercise.
At home:
- Use an indoor air quality monitor to track PM2.5 and CO2 levels in real time.
- Use in tandem with an outdoor air quality monitor to know when outdoor air could impact indoor air quality.
- Open windows when outdoor air quality is good. Close them when it is poor.
- Avoid exercising near high-traffic hours or in areas with heavy cleaning fumes.
Conclusion
Clean air is a non-negotiable component of an effective workout. By choosing cleaner spaces, monitoring air quality, and pushing for better standards, you can breathe easier and perform better.
Take a breath during your next workout—and make sure it’s a clean one.
