Importance of Air Quality in Gyms

Air Quality in Gyms

Updated on:

December 11, 2025

When you walk into a gym, you expect a boost to your health, not an invisible hit to your lungs. Yet air quality in gyms can be surprisingly poor, especially in crowded, poorly ventilated spaces. Research shows that air pollution contributes to millions of premature deaths worldwide every year, mainly through heart and lung disease, making it one of the leading global health risks.

This matters during exercise because you breathe faster and deeper, pulling more pollutants into your body with each workout. The good news: with basic awareness and affordable monitoring tools, you can significantly reduce the risks without giving up your training routine.

What Pollutants Are You Breathing in at the Gym?

Indoor air quality in gyms is often a mix of carbon dioxide from people, particles from dust and chalk, chemicals from cleaning products, and airborne microbes. Studies consistently find elevated levels of CO2, particulate matter (PM), and volatile organic compounds (VOCs) in fitness centers, sometimes above recommended values for comfortable and healthy indoor environments.

A recent review of air quality in fitness centers found that gyms frequently show high indoor concentrations of CO₂, PM2.5, PM10, VOCs, and formaldehyde, especially during peak hours. Another study in health clubs reported that exercising in these environments can lead to increased exposure to fine particles and gases linked to respiratory and cardiovascular effects.

Carbon dioxide (CO₂): A signal of stale, crowded air

CO₂ itself, at the levels typically found in gyms, is a proxy for how much exhaled air is building up, not the main toxic agent. High CO₂ means you’re rebreathing other people’s air and that fresh outdoor air isn’t coming in fast enough.

Many building practitioners use around 1,000 ppm as an informal upper limit for “acceptable” indoor air quality, even though the ASHRAE ventilation standard does not set a hard CO₂ limit.
ASHRAE guidance suggests indoor CO₂ ideally should not exceed about 700 ppm above outdoor levels.
Practical guidance for comfort and cognition often recommends aiming for ~800–1,000 ppm when a room is occupied.

If your gym regularly sits at 1,500–2,000 ppm or more during classes, that’s a sign of inadequate ventilation and a higher probability that other pollutants and bioaerosols are also accumulating.

Particulate matter (PM2.5 and PM10): Dust, chalk, and resuspended dirt

Particulate matter (PM) includes tiny solid and liquid particles that can reach deep into the lungs. The World Health Organization (WHO) now recommends an annual average PM2.5 limit of 5 μg/m³ and a 24-hour average of 15 μg/m³ to reduce health risks.

In gyms, PM2.5 and PM10 can come from:

Resuspended dust from floors and mats (especially with high foot traffic).
Chalk and rubber particles in weightlifting or climbing areas.
Outdoor pollution leaking indoors.

A study of a school gym found that coarse PM (between PM10 and PM2.5) increased significantly during sports activities and closely followed the number of people exercising, indicating that human activity itself drives particle spikes.

Research also shows that physical activity in sports facilities can raise indoor PM concentrations by up to 300%, and CO₂ levels frequently exceed 1,000 ppm in inadequately ventilated spaces.

VOCs, formaldehyde, and cleaning chemicals

Volatile organic compounds (VOCs) and formaldehyde in gyms typically come from:

Cleaning and disinfectant sprays.
Air “fresheners” and scented products.
New flooring, paints, and equipment off-gassing.

A large survey of fitness centers reported high VOC and formaldehyde levels, suggesting that chemical exposure may be significant alongside physical benefits. Chronic exposure to certain VOCs is associated with headaches, eye and throat irritation, and, at higher or prolonged levels, increased risks of asthma and other respiratory issues.

Bioaerosols and infections: When heavy breathing spreads more than endorphins

Exercise increases not just how much air you breathe in, but also how many particles you breathe out. Laboratory research shows that intensive endurance exercise can increase aerosol particle emission by more than 100-fold compared with rest, raising the potential for airborne disease transmission during group workouts.

In a poorly ventilated studio, that means exhaled viruses and bacteria can accumulate quickly—especially during high-intensity classes where everyone is breathing hard.

Air Quality & Your Workout: The Hidden Performance Killer

Poor air quality in gyms doesn’t just threaten long-term health; it can quietly reduce how strong, fast, and focused you feel during a single workout. When pollutant levels are high, your body must work harder to get the same amount of oxygen and manage inflammation, which can raise perceived exertion and reduce endurance.

What happens to pollutants during exercise?

During exercise, your minute ventilation (the amount of air you breathe per minute) and depth of breathing increase significantly. One classic study of ultrafine particles found that the total number of particles deposited in the lungs was more than 4.5 times higher during exercise than at rest, due to both higher breathing rates and a higher fraction of each breath being deposited in the lungs.

Reviews of particle deposition similarly conclude that deposition fractions nearly double from rest to intense exercise, meaning your lungs effectively become more “sticky” to particles when you work harder.

In other words, a level of pollution that might be tolerable when sitting at a desk can deliver a much higher effective dose when you’re doing burpees or sprint intervals.

Immediate effects you might feel during a workout

Even when values are below acute danger thresholds, you might notice:

“Heavy” or tight chest, especially for people with asthma or allergies.
Headaches, dizziness, or unusual fatigue in crowded studios with high CO₂..
Coughing, throat irritation, or burning eyes when PM or cleaning fumes are high.

Studies on exercising in polluted environments report blunted improvements in lung function and signs of inflammation when people train at PM2. 5 levels significantly above recommended limits

Long-term health risks: The big picture

Globally, air pollution is estimated to contribute to about 7.9 million deaths in 2023, making it the second leading risk factor for early death after high blood pressure. In the European Union alone, fine particulate matter (PM2.5) was linked to around 182,000 premature deaths in 2023.

Most of this burden comes from chronic exposure over years, not a few gym visits. But if you regularly train in spaces with poor air quality, those exposures can become part of your long-term risk profile—especially if you already have cardiovascular or respiratory conditions.

Is It Safe to Work Out Indoors With Bad Air Quality?

In many cases, yes—exercise still offers major health benefits, but you should be smart about how and where you train. US EPA guidance for particle pollution (PM2.5) and the Air Quality Index (AQI) suggests that sensitive groups should reduce or avoid intense outdoor exercise at AQI values corresponding to 24-hour PM2.5 above about 35 μg/m³, and most people should limit intense activity when levels exceed around 55 μg/m³.

Although these thresholds are defined for outdoor air, they provide a useful reference for indoor gym readings if you use a portable PM2.5 monitor:

If PM2.5 is <15 μg/m³ (near WHO’s 24-hour guideline), conditions are generally good for exercise.
Between 15 and 35 μg/m³, most healthy adults can still work out, but people with asthma or heart disease may prefer lighter sessions or shorter duration.
Above 35–55 μg/m³, sensitive groups should strongly consider reducing intensity or relocating.
Above 55 μg/m³, it’s reasonable for almost anyone to question whether this is the right environment for intense training.

From a CO₂ perspective, if indoor levels are consistently above 1,500–2,000 ppm during your workout, that strongly suggests poor ventilation. While these concentrations are not acutely toxic on their own, they may contribute to sleepiness, headaches, and an increased proportion of rebreathed air, including exhaled aerosols.

Bottom line: for most healthy people, the benefits of exercise still outweigh the risks at low to moderate pollution levels, but if your gym’s air consistently looks “unhealthy” on a monitor, it’s worth changing something—location, time of day, or your gym’s ventilation strategy.

Gym Air vs. Outdoor Air: Which Is Worse for Your Lungs?

It depends on where you live, how your gym is built, and what the outdoor air is like that day. In some polluted cities, outdoor PM2.5 can regularly exceed WHO guidelines by several times; in others, outdoor air is relatively clean.

A modelling study of outdoor physical activity suggested that for a typical urban background PM2.5 concentration of 22 μg/m³, the health benefits of moderate physical activity still outweigh the pollution risks for the general population.

However, indoor sports environments like gyms and arenas have been shown to:

Sometimes have higher coarse particle levels than outdoors due to resuspension from floors and equipment.
Show elevated CO₂ and PM during peak usage, particularly in smaller or poorly ventilated studios.

How to decide where to work out:

If the outdoor AQI is good or moderate and your gym feels stuffy, a run in a green area may actually be the cleaner choice.
If outdoor AQI is poor (e.g., wildfire smoke or heavy smog), a well-ventilated gym with good filtration is likely safer for your lungs than exercising outdoors.
In both cases, measurement matters: a small PM2.5 and CO2 monitor can tell you quickly which option is better that day.

Is Your Gym Properly Ventilated? (Signs of Stale Air)

A well-ventilated gym should feel fresh, not like you’re breathing the same air as yesterday’s spin class. While you can’t see air changes directly, you can spot warning signs that the ventilation system isn’t keeping up.

Quick signs of poor ventilation and bad air quality in gyms:

Persistent “sweaty” or chemical smells that don’t clear between classes.
Fogged mirrors or condensation on windows despite normal temperatures.
Feeling unusually drowsy, headachy, or “heavy” within 20–30 minutes.
Tight, humid air with little sense of movement, especially near ceilings.
A CO₂ monitor that regularly reads >1,200–1,500 ppm during peak times.

Ventilation standards from organizations like ASHRAE are based on providing a minimum flow of outdoor air per person and per square meter, but many existing gyms may not meet them in real life—especially after renovations or changes in occupancy.

Why humidity matters too

Relative humidity (RH) influences both comfort and infection risk. Reviews of indoor air and health suggest that keeping indoor RH between 40% and 60%:

Supports our respiratory immune defenses and mucosal barrier.
Reduces the viability and transmission of some viruses and bacteria.
Minimizes issues like dry eyes, irritated airways, and mold growth.

If your gym is consistently very dry (e.g., <30% RH) or very humid (>70% RH), that can amplify respiratory irritation or drive mold and dust mites.

How Can You Track Gym Air Quality in Real Time?

You don’t need a lab to understand air quality in gyms. Affordable sensors now make it possible to carry a mini air lab in your pocket.

Key metrics to monitor

CO₂ (carbon dioxide)
- What it tells you: how much exhaled air is accumulating, a proxy for ventilation and crowding.
- Practical targets: aim for ~800–1,000 ppm during workouts; sustained values above 1,500–2,000 ppm suggest poor ventilation.
PM2.5 and PM10 (particulate matter)
- What they tell you: dust, smoke, and other airborne particles that can reach deep into the lungs.
- Targets: aim to stay as close as possible to WHO’s 24-hour PM2.5 guideline of 15 μg/m³, and try to avoid long workouts when levels are in ranges considered “unhealthy for sensitive groups” or higher by AQI frameworks.
VOCs (volatile organic compounds)
- What they tell you: presence of chemical vapors from cleaners, off-gassing materials, and fragrances.
- Many consumer sensors provide an index rather than precise concentrations. Watch for sustained high readings or spikes after cleaning. Fitness-center studies show elevated VOC levels can be common, especially in small studios.
Temperature and relative humidity (RH)
- Aim to keep RH roughly 40–60% for comfort and reduced infection risk, based on multiple health and building science reviews.

Tools you can use

Portable multi-sensor monitors that measure CO₂, PM, VOCs, temperature, and humidity, often syncing with a smartphone app.
Wearable or keychain-sized devices that track CO₂ or PM2.5 while you move around the gym.
Wall-mounted CO₂ displays that gyms can install so both staff and members can see real-time ventilation status.
Outdoor AQI apps (from national or local agencies) to help you decide whether to exercise indoors or outside on a given day.

How to use these readings in practice

On arrival: Take a quick CO₂ and PM2. 5 readings in the main workout area.
During peak times: If CO₂ climbs well above 1,500 ppm or PM2.5 jumps into “unhealthy” ranges, consider moving to a quieter corner, switching to lighter activity, or reducing workout duration.
Over weeks: Share repeated high readings with gym management; good managers often want this feedback but lack data.

Conclusion: Making Every Workout Safer to Breathe

Air quality in gyms is not something you can see on the treadmill display, but it has a real impact on your lungs, heart, and performance. During exercise, you inhale more deeply and more often; if the air is polluted, you receive a higher dose of particles and gases than you would at rest.

You don’t need to become an air-quality engineer, but you can:

Notice basic signs of poor ventilation.
Use simple monitors to check CO₂ and PM2.5.
Choose spaces, times, and gyms that treat fresh, clean air as part of fitness—not an optional extra.

Think of air quality as part of your training plan, alongside sleep, nutrition, and recovery. When the air is cleaner, your workout doesn’t just feel better—your body can reap more of the benefits you’re working so hard for.

FAQs: Air Quality in Gyms & Exercise

1. Is it safe to work out indoors with bad air quality?

It depends on how “bad” the air is and your health status. For most healthy adults, exercise still offers net health benefits at low to moderate pollution levels, but when PM2.5 or CO₂ is very high, especially if you have asthma or heart disease, it’s wise to shorten, lighten, or relocate your workout.

2. What is the indoor air quality in gyms typically like?

Research in fitness centers often finds elevated CO₂, PM2.5/PM10, and VOCs, especially during busy periods, and sometimes above recommended guidelines for comfortable and healthy indoor spaces.

3. What CO₂ level is safe in a gym?

CO₂ is best seen as a ventilation indicator rather than a toxin at typical gym levels. Many experts recommend aiming for ~800–1,000 ppm during occupancy and treating sustained levels above 1,500–2,000 ppm as a sign of poor ventilation and crowded conditions.

4. What PM2.5 level is too high for exercise?

WHO recommends ≤15 μg/m³ as a 24-hour PM2.5 guideline. AQI frameworks consider >35 μg/m³ as “unhealthy for sensitive groups” and >55 μg/m³ as “unhealthy” for the general population, at which point intense exercise should be reduced or moved.

5. How can I tell if my gym has poor air quality without a monitor?

Look for stale smells, condensation on windows, visible dust in sunlight, headaches or unusual fatigue, and stuffy rooms that feel worse during peak times. These clues cannot replace measurements, but they often indicate inadequate ventilation or cleaning practices in line with research on indoor environments.

6. Do air purifiers really help in gyms?

Yes—properly sized HEPA air cleaners with good airflow can significantly reduce indoor particle levels, especially in smaller rooms, provided filters are maintained and devices do not generate ozone.

7. Are group classes riskier than solo workouts for infections?

Often, yes. Intensive group exercise can increase aerosol particle emission by more than 100-fold compared with rest, which can raise the risk of airborne disease spread if ventilation and filtration are inadequate.

8. Should people with asthma or heart disease avoid certain gyms?

People with asthma, COPD, or cardiovascular disease are more sensitive to pollution. Guidelines suggest they should limit intense activity when PM2.5 or AQI categories reach “unhealthy for sensitive groups” and above. For these individuals, choosing gyms with visible ventilation, cleaner measurements, and lower crowding is particularly important.

9. How often should gyms check their air quality?

Ideally, gyms should continuously monitor CO₂ and regularly log PM2.5, temperature, and humidity, especially in high-use areas. Reviews of fitness center environments recommend ongoing monitoring as part of a health-oriented indoor air strategy.

10. What can I ask my gym to do about air quality?

You can politely ask management to:

Share their ventilation and filtration strategy.
Install or display CO₂ monitors in studios.
Use low-VOC cleaning products and limit strong fragrances.
Consider HEPA air cleaners in crowded rooms.

These requests align with best-practice recommendations from building and public health research on sports facilities.

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