Should you leave the air purifier on all day?

Globally, indoor and outdoor air pollution are one of the leading risk factors for death. Sources of outdoor air pollution can include fires, cars, or power plants just to name a few. Indoor air pollution can come from cooking, industrial byproducts, mold, or many other sources.

As a result, if you want to remove or destroy airborne pollutants indoors, running an air purifier will reduce contaminant levels. There are many sources of pollutants and some may be out of your control. To receive the full benefit of a purifier, it’s best to keep it running and change the filters on time.

All homes exchange air with the outdoors

No home is completely sealed against outdoor air and outside pollutants. Not only does the moisture from cooking and bathing have to get out, but the carbon dioxide from breathing does too. Buildings run the gamut from poorly sealed enclosures that let in the wind and let out heat, to what are known as “tight” homes that allow very little ventilation. 

Modern buildings tend to follow regulations that recommend a certain number of air changes per hour (ACH), which is a measure of how much ventilation a room has. One air change is when enough outdoor air is ventilated into the room to displace the air inside the room. ACH assumes that air in a room is well-mixed so all of the inside air is displaced at the same rate and there aren’t any stagnant spots where air doesn’t flow. Ventilation occurs via one of three mechanisms: natural ventilation like open windows, mechanical ventilation like ducts, and leakage around windows, doors, or anywhere else.

The ACH of your home can have a huge impact on pollution levels depending on the source of the pollution. If your home has a low ACH, it exchanges very little air with the outdoors which may have the following benefits:

  • Outdoor air pollutants such as wildfire smoke, car exhaust, or pollen will enter the home at a lower rate
  • Air conditioning, ventilation, and heating systems are more efficient and effective

However, there could also be problems with having a low ACH in your home. Specifically, the following are problems that need to be solved with ventilation:

  • Accumulation of fumes or smoke from cooking
  • Accumulation of chemical byproducts from furniture or building materials
  • Accumulation of carbon dioxide, making the air stale
  • Excessive moisture can’t leave the building and mold may grow

Most modern dwellings (built after 2000) are designed to have an ACH of about 0.35 per hour. This ACH is low compared to older buildings in order to make climate control systems more efficient, which is generally beneficial for both the occupant and the planet. Most buildings that are considered “green” have a low ACH so they require less energy to keep comfortable.

Mechanical ventilation is often used to increase the ACH on demand. In homes, this is very common with a fan above the stove. It’s always a good idea to turn the fan on when cooking to increase ventilation to remove any fumes or smoke. Many bathrooms also have either a fan for mechanical ventilation or a window for natural ventilation. When taking a shower it’s usually a good idea to increase ventilation or moisture can accumulate and mold could grow.

Air purifiers add clean air

Air purifiers don’t ventilate a home with outdoor air.  Instead, they can help with some of the problems that arise from low ventilation. Almost all air purifiers have an ACH rating, but the ACH provided by air purifiers is not the same as the ACH provided by ventilation with outdoor air. This is because air purifiers remove contaminants instead of diluting them with outdoor air.

There are a few different reasons why air that has been cleaned by an air purifier is different from outdoor air. For one, a purifier works with indoor air, so outdoor air pollutants won’t enter the home as with ventilation. The air from a purifier has the potential to be cleaner than outdoor air in some parts of the world.

Air purifiers don’t impact every component of the air. Moisture and carbon dioxide, two of the most important reasons to ventilate, are not typically removed by air purifiers. Removal of moisture without outside ventilation requires a dehumidifier. Removal of carbon dioxide without ventilation requires a specialized scrubber that is typically used in sealed environments like submarines.

Air purifiers are best at removing particles such as smoke, dust, pollen, or mold spores that are in the air, and most filters have an activated carbon layer to remove chemicals. All our Molekule air purifiers use PECO technology to clean the air, which both captures large particles and destroys chemicals, viruses, and bacteria.

Be sure that any air purifier you use does not produce ozone, which is toxic and will not improve the air. The California Air Resources Board maintains a list of air purifiers that are ozone safe.

Run your air purifier all the time

Since air pollution is a pervasive and continuous problem, it’s best to leave your air purifier on all day. There are no perceived drawbacks to keeping your unit running all the time, and if the filters are changed on time it can help to reduce pollutants in the home. Do keep in mind that sometimes ventilation with outdoor air is the easiest and quickest way to reduce indoor pollution.

There are many reasons why air purifiers are preferred over ventilation with outdoor air, the most common being for anyone who lives anywhere without consistent good weather. Bringing in outdoor air when the heat or air conditioner have been running is a waste of energy. People with allergies may want to avoid being exposed to outdoor air and pollen that comes with it. Also, with new building codes requiring rooms with low outside ventilation, air purification can be a great way to reduce pollutants.

We hope you stay tuned to this blog to learn more about indoor air quality and what you can do to keep yours in good shape.

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