Should I Turn Off My Air Purifier At Night Or Leave It On?

So you brought the latest and most powerful air purifier on the market. Everything looks great and the air is being filtered as we speak. Your allergy symptoms have gone and overall indoor air quality has improved. Yet, there is the question that always has been lingering in your head. Am I suppose to leave the air purifier on all the time or let it cool down to avoid overheating? What about the electricity cost?
Short answer
Leave it on all day, every day.


Can You Leave Air Purifier On All The Time?

You should leave your air purifier on all the time to ensure there is a constant flow of purified, clean air. When the air purifier is turned off, it will stop filtering the air thus harmful particles like dust, pet dander, mold, pollen, bacteria, viruses will gradually return within 2 to 4 hours. The health effects of air pollution are pervasive but the risk can be reduced when the air purifier is kept on. The only time you should not be running an air purifier is when there is a safety hazard such as a damaged power cord, dirty filters, or the presence of an ozone generator that diffuses harmful ozone.

can you leave air purifier on all the time

Should I Sleep With Air Purifier On?

Yes, you should. As we spend about one-third of our life sleeping in the bedroom, keeping an air purifier on during bedtime can improve your sleep quality and overall health according to The Asthma and Allergy Foundation of America (AAFA). With an air purifier continuously removing airborne contaminants while you sleep, you will be at less risk of breathing into the allergens and wake up feeling refreshed the next day. When the air purifier is turned off, airborne allergens will build up overnight and can disrupt your sleep by triggering allergic reactions e.g. night cough, choking, sinus. Note that not all air cleaners are suitable for nighttime use because of the loud fan noise. To find out which model does, visit the best bedroom air purifiers that we reviewed recently here.

Should I Leave My Air Purifier On When I’m Not Home?

Yes, you should leave your air purifier running when you’re not at home to ensure airborne particulates are always removed. You will be greeted with clean, fresh air when you return from work or holiday rather than having to wait for the air purifier to restart the cleaning cycle. It is not possible for the room air quality to remain clean with only a couple of hours of runtime.

Is It Safe To Run An Air Purifier All The Time?

It is perfectly safe to leave a HEPA air purifier on day and night as it is designed to run 24×7 without overheating, breaking down, or releasing harmful byproducts. Most models are also CE/ UL listed with strict safety compliances, children/ pet friendly, and CARB certified to be ozone-free. Just remember to clean the pre-filter every 2-3 weeks and replace the HEPA/ carbon filters accordingly to maintain its filtration efficiency.

Is It Safe To Run An Air Purifier All The Time?

Is It Costly To Run An Air Purifier All Day?

It is not costly to run an air purifier all day every day compared with other home appliances. It will only cost you an estimate of $0.08 to $0.30 dollars daily depending on the airflow speed, power wattage, and states you're in. Some model even has a power consumption rate equivalent to a light bulb. Regardless of how long the air purifier is running, you will not see a huge spike in your electric bills.

We do not recommend running an air cleaner intermittently in order to save cost. It is far from economical and you will be at risk of inhaling harmful contaminants when the air purifier is off. The air cleaner will also have to work extra hard to restore back the clean air and may end up using more energy. Instead, pick an Energy Star Rated air cleaner or model that comes with an energy-saving Auto mode that only uses higher fan speed when there is a high concentration level of pollutants detected.

To calculate the running cost of an air purifier, multiply the energy consumption with the rate of electricity (by states) and hours of operation. For the monthly electricity bill, multiply the cost by 30 days.

Should I Open Windows With An Air Purifier On?

With an air purifier turned on, you should keep all windows shut to reduce the number of irritants from flowing in. Even if outdoor air is not polluted, leaving windows open forces the air cleaner to work harder as unfiltered air will keep on coming in and clean air continues to flow out.

When Should I Turn On My Air Purifier?

Whenever possible but the best time to turn on an air purifier is when you step foot in the home. Run it at the highest speed for at least an hour to remove the lingering airborne pollutants before switching it back to normal speed or auto mode. Again, we highly recommend you leave the air purifier on and never switch it off unless you intend to move the device elsewhere.

Optimizing An Air Purifier That Runs All-day

Airborne pollutants do not take a break while you sleep or not around. While opening windows is the quickest and easiest to improve indoor ventilation, it is not a long-term solution and is less effective compared with an air purifier. That said, if you plan to run an air purifier day and night, it is important to check on the filter condition regularly. A dirty filter is less effective as more and more particulates are trapped inside. The below steps will also help extend the air purifier usage life and help improve indoor air quality. Every little bit of effort counts.

  • Only choose a mechanical HEPA air purifier over a standalone ionizer or UV sanitizer. Never go with an Ozone generator that produces harmful ozone.
  • Replace the HEPA filter and carbon filter when the filter change indicator is flashing typically between 6 to 12 months.
  • Keep your home clean and tidy by vacuuming regularly to reduce the air purifier workload.
  • Pick the right size air purifier e.g. tabletop, tower where you can place it at a comfortable location.
  • Make sure the air purifier's suggested room size is adequate at a minimum of 2 air changes per hour. Ideally, the CADR should be at least 200 cubic feet per minute.
  • Ensure the air purifier noise level is at an acceptable level that you can live with it.



Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.
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