Should you keep your air purifier on at all times?

In this article, we will discuss whether an air purifier should be left on at all times. Furthermore, we will discuss the advantages as well as the limitations of doing so, and under what circumstances is it ideal to leave your air purifiers on at all times.

Should you keep your air purifier on at all times?

Yes, you should leave your air purifiers on at all times, in a general circumstances. Air pollution is a pervasive problem and is continuous in nature. 

Air purifiers are devices that filter out undesirable particles and dust from the ambient indoor air. In other words, they clean the air.

Over the past years, air pollution has worsened with time, owing to human activities such as deforestation, industrialisation, rapid urbanisation, and so on. 

An average American spends more than 90% of their time indoors, with more than 80% of it being inside buildings.

In large cities, due to traffic-related pollution, there is a chance that the indoor air is more polluted than the outdoor air. This can have serious implications to health.

Among these pollutants, the most dangerous is particulate matter (PM). These include particles such as dust, soot from combustion-related activities, animal dander, pollen, industrial exhaust, and so on.

Several studies have shown the adverse effects of particulate matter on cardiovascular system and the respiratory system, and has proven to be the reason to cause premature deaths for people with pre-existing medical conditions.

This is where air purifiers come in handy. They filter out particulate matter less than 0.3 microns, and the HEPA (High Efficiency Particulate Air) filters typically have an efficiency of more than 99%.

Given the prevalent nature of particulate matter in our surroundings, it is wise to keep the air purifier on at all times.

Circumstances under which you should keep your air purifier on at all times

We will discuss situations for which it is essential to keep your air purifier running at all times

If your house is located near a road

Over the past few years, traffic-related pollution has been a major contributor to air pollution. With the increase in the number of vehicles each year, the problem will worsen. 

Traffic-related pollution refers to the pollution generated by activities such as fumes generated from burning of fuel, braking of vehicles which causes suspension of road dust and rubber released from the normal wear and tear of the tyre.

One of the major pollutants generated from this activity is soot, also known as black carbon, since it absorbs and entraps radiation.

Soot is an amorphous particulate matter composed entirely of carbon, and is generated due to incomplete combustion of fuel.

Other than its implications on global warming, black carbon also has serious health implications. It can act as an adsorbent, meaning that it allows other substances to settle on its surface. 

Typically, these are heavy metals like lead (Pb), which can exacerbate the effects if inhaled.

Therefore, if your house is located near a road, especially if the area is prone to traffic congestion, you must leave your air purifier on at all times.

If your house has a mold problem

Molds refer to the fungal growth that occurs under conditions such as low temperatures and high relative humidity levels. They tend to grow on areas such as walls, drywalls, areas with leakage issues, clothes, footwear, furniture, and so on.

Molds propagate to other places by creating spores, which are submicron particles that are usually harmless, albeit they cause allergic reactions.

However, certain species of mold are highly toxic, such as black mold, which causes the black fungus illness, which can be lethal if not treated effectively.

Air purifiers are your best bet to fight against mold. However, a drawback is that mold develops in damp places, and humid air is ‘heavy’ in nature.

This causes an additional load for the air purifier for working, and can reduce its effectiveness, especially for air purifiers with HEPA filters. 

The best solution for this problem would be to pair up your air purifier with an air dehumidifier, as that would also help to keep the humidity levels of the room in check, which in turn would hinder the growth of mold.

If you own a furry pet 

Furry pets such as dogs and cats are also potential contributors to indoor air pollution. The dander and hair cause allergic reactions, and in seasons where the rate of fur shedding increases, the problem gets much worse.

Sometimes, certain microorganisms such as bacteria or viruses can also get entrapped within the dander, and can have serious health implications.

For people with pre-existing respiratory illnesses, their ailments can get flared up and could even worsen with time. Therefore, it is vital to keep the air purifier on at all times, as it rids the indoor air of dander and hair, keeping the air clean.

If you or another occupant suffer from a respiratory illness or are immunocompromised

Immunocompromised is a term used to refer to people whose immune systems do not function adequately, due to genetic or environmental factors. 

Respiratory illness include ailments such as asthma, bronchitis, Chronic Obstructive Pulmonary Disease (COPD), and so on.

Under such conditions, if a person is exposed to air pollution, their body would not handle it efficiently, which in turn could cause adverse health issues.

For such people, it is crucial to maintain a healthy standard of indoor air quality. Hence, it is wise to leave the air purifier on at all times.

Advantages of keeping air purifier on at all times

We shall discuss the advantages of keeping an air purifier on at all times below

Maintains an odorless environment

The biggest advantage of keeping the air purifier on at all times is that it keeps the air clean and removes odors.

Many household activities give rise to undesirable odor, such as smoke, kitchen discards, and so on. This decreases the aesthetic appeal of the indoor air. Therefore, it is ideal to keep the air purifier on under such circumstances.

Removes Volatile Organic Compounds (VOCs)

VOCs refer to a variety of organic compounds that are emitted from certain materials in the form of a gas. These compounds are present in common household items, such as paints, solvents, cleaning products, cosmetics, and fuels. 

Studies have shown that continuous exposure to VOCs can increase the odds of getting cancer. Therefore, an air purifier should be kept on at all times, preferably in areas where VOC-emitting items are kept.

Energy efficiency

Even in the dead of winter, air purifiers are a cost-effective method to make your house more ventilated, hotter, and less dependent on other energy sources. 

An air purifier might help you save money on other energy-intensive utilities. The HEPA channels let them function more quickly and efficiently, which may help you budget for your electricity and utility expenditures.

Helps to maintain a smoke-free environment

Cigarette smoking is not only bad for the smoker’s health, but also for people being exposed to the smoke. The association between secondhand smoking and risks of getting cancer is well-documented in several studies.

Therefore, it is vital to ensure that the indoor air is devoid of smoke. Air purifiers not only filter out the toxins present in the smoke, they also help to get rid of the smell of smoke.

Limitations of keeping air purifier on at all times

So far, we have seen situations in which leaving an air purifier on at all times is beneficial for the indoor air quality, therefore for the occupants.

However, there are certain drawbacks of leaving your air purifier on at all times,  and we shall discuss them below.

Efficiency  decreases much faster with time

Although air purifiers are advertised as devices that can be kept on at all times, it is not the case. Keeping the air purifier on at all times will increase the workload on the device, causing its efficiency to decline much faster with time. 

This will cause problems such as inability to effectively remove smaller particulate matter, allergens, and other particles. 

Exposure to ozone gas

Ozone is a gas that is naturally formed by interaction of light with oxygen molecules. It is a vital gas in the upper atmosphere, where it blocks the harmful UV rays from entering the atmosphere.

However, when present at the ground level, it has negative implications on human health. 

A serious drawback of keeping your air purifier on at all times is the emission of ozone, which is generated as a byproduct in the process. 

The characteristic pungent odor of ozone can irritate the inner linings of the airways and can trigger an asthma attack. However, ozone is an unstable molecule, and it can attack the DNA, causing impairment of cellular function.

Various studies have shown that ozone can have adverse effects that include functional,morphologic, immunologic, and biochemical alterations.

A breeding ground for mold and bacteria

For cases where the air purifier is installed in rooms with high relative humidity, one of the common substances to get trapped in the air filter would be mold and bacteria.

If the filter is left on at all times, the amount of water vapour that gets entrapped in the filter will also increase.

Not only will this reduce the efficiency of the filter, it will also serve as a breeding ground for mold and bacteria, which in turn would be propagated through the air purifier.

So, it is vital to install a dehumidifier along with the air purifier, and to regularly check the filter for the presence of mold or other bacteria.

UV Rays 

UV rays in a filter kill all the particulate matter that passes through it. UV technology is commonly combined with air filters to attain efficiency and maximum air quality.

Facts are also astonishing for humans as the filter fixed with UV technology also tends to break the oxygen and water molecules into ozone and hydroxyl. The broken down elements will then react with other pollutants and turn even more harmful.

UV air purifiers, thus, may not be an effective solution for particulate matter. Many UV air purifiers miss out on trapping microorganisms because of shielding provided by the particles.


It is vital to keep your air purifier on at all times. It helps to get rid of the odors, which reduce the aesthetic appeal of the house.

Furthermore, keeping air purifiers on at all times helps to filter out the particulate matter and other chemical species that can be present in the indoor air, all of which could have serious implications in human health in various manners.

Lastly, we talk about the drawbacks of keeping the air purifier on at all times, as its efficiency could rapidly decrease, increased amount of ozone in the indoor environment, act as a breeding ground for mold and bacteria, and the UV Rays which can create compounds harmful for our health.


Wouldn’t keeping the air purifier on at all times consume a lot of electricity?

No, keeping the air purifier on at all times does not consume a lot of electricity. Air purifiers are energy efficient and require low power for operation. 

Furthermore, in the present scenario, air purifiers are as essential as certain appliances such as refrigerators. Hence, it is necessary to keep it on at all times.

Should I keep my air purifier on at night?

Yes, you should keep your air purifier on at night. When you’re sleeping, your body is repairing itself from the daily wear and tear. By keeping your air purifier off, you expose yourself to a greater risk of being adversely affected by air pollution.

Other FAQs about Air Purifiers and Filters that you may be interested in.

HEPA Filter: What do you need to know?

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