A bedroom’s air quality is important for getting a good night’s sleep. Many people rely on air purifiers to rid their sleeping quarters of dust mites, microbes and other airborne particles, as well as bacteria, viruses, volatile organic compounds (VOCs), and unpleasant odors. Air purifiers are particularly beneficial to people with allergies and/or asthma. Air purifiers sold today fall into four general categories based on the type of filtration used: HEPA, activated carbon, ionizer, and ozone; some purifier models utilize more than one of these systems, as well as UV technology. Although high-end air purifiers can cost hundreds of dollars, shoppers can usually find models for $100 or less.
This guide will explore the purpose and functionality of air purifiers, some benefits and disadvantages of using one, tips for first-time buyers, and our picks for the top-rated air purifiers according to actual owners.
Air purifiers remove contaminants and irritants from indoor air using one of two general techniques:
- Active purification, which uses a process known as ionization to convert chemicals and gases into harmless molecules. This process does not remove contaminants, which makes it somewhat inefficient compared to passive purification.
- Passive purification, which removes pollutants from the air using a filtration system. This is considered the more efficient system since contaminants are permanently removed from the air, rather than converted.
Most air purifiers sold today utilize one (or more) of the following four technologies:
HEPA: An acronym for High Efficiency Particulate Air, HEPA is a filtration system that must (according to industry standards) trap at least 99.7% of particles larger than 0.3 microns, which include chemicals, spores, and other particles that cannot be seen with the human eye.
HEPA filters are accordion-shaped and made of ultrafine fibers. They use three processes to trap particles of different sizes:
- The first process is interception. Large particles are trapped immediately, and smaller particles that come within a certain distance will be sucked in and held in place with an adhesive.
- The second process is the impaction, during which smaller particles attach themselves to larger particles that are already stuck to the filter.
- The third process is the diffusion, which essentially slows down smaller particles and causes them to come into contact with gas particles. This is considered the last resort; most particles are trapped using interception or impaction.
Particles accumulate on the filter whenever air passes through, resulting in cleaner air each time. Larger particles are immediately trapped, while smaller ones HEPA filters generally need to be replaced every two to four years; replacement filters are widely available.
HEPA filters are considered the most effective air purifiers for removing particles, as well as the most common and, in most cases, the cheapest. However, they do not remove odors or volatile organic compounds (VOCs), which are emitted from paint, adhesives, and other gas pollutants. One important note: some purifiers advertise as using ‘HEPA-like technology’ or use similar verbiage, but this usually means the filters do not meet official HEPA standards.
Activated carbon: ‘Activated carbon’ (also known as activated charcoal) refers to a form of carbon that has been modified with small, porous openings that expand its surface area. Active carbon technology employs filters that feature low-volume pores that are extremely absorbent.
As a result, activated carbon purifiers trap odors, VOCs, and other emissions that cannot be trapped by HEPA filters. However, they are less efficient when it comes to trapping dust mites, microbes, and other air particles. For this reason, some purifiers feature HEPA and activated carbon filters.
Ionizer: Also known as negative ion purifiers, ionizers rely on active purification (unlike HEPA and activated carbon purifiers that use the passive method). Ionizers essentially zap particles with a chemical charge and collects them using one of two methods:
- The particles are drawn to the purifier, where they can be wiped off.
- The particles collide with other particles, which causes them to gain weight and eventually become unable to float; they may then be swept up or vacuumed.
This method, while scientifically advanced, is somewhat inefficient because it transfers particles to other areas of the room, rather than absorbing them or trapping them in a filter. This poses the risk of the particles breaking free and reentering the air.
Ozone: Ozone purifiers clean the air using ozone gas. This technology is controversial because ozone, when produced at high levels, can be toxic to humans. Long-term exposure to smaller amounts can also lead to health problems. As a result, ozone purifiers have not received official approval from any federal safety oversight agency — although, for the record, much of the bad press comes from purifier brands that use different technologies.
The upside to ozone purifiers is that they are highly effective at transferring molds, bacteria, odors and gases — but not dust or other particles. As a result, ozone purifiers often feature ionizers as well.
In addition to the four technologies described above, some purifiers — typically passive, filtration models — utilize UV technology. UV uses active purification to convert oxygen particles into ozone, which then targets bacteria and viruses and converts them into harmless molecules. However, this technology is not particularly effective at targeting allergens.
The table below summarizes the key differences between HEPA, active carbon, ionizer, ozone, and UV purification technology:
|Type of Purification||Passive||Passive||Active||Active||Active|
Regardless of the technology used, air purifiers commonly feature the following components:
- A timer that can be programmed for certain intervals.
- Adjustable speeds, which include lower settings for quieter purification and higher settings for more effective purification.
- Manual or remote controls. Most purifiers sold today feature the former.
The following components are associated with certain purification technologies:
- HEPA and activated carbon purifiers feature a filter, which may need to be changed every six months to two years, depending on the model; some models feature washable filters, but these are considered less effective. These purifiers also have an indicator light that lets owners know when the filter needs to be replaced.
- HEPA and activated carbon purifiers use a fan to draw in particles, bacteria, and other contaminants, where they become stuck to the filter.
- More advanced HEPA and activated carbon purifiers are equipped with contaminant sensors that automatically adjust the settings based on how dirty or clean the room is.
- Active purifiers feature an ionizer (see above), which hits contaminants with a chemical charge and either removes (but does not eliminate) them from the air or converts them into harmless molecules.
Purifiers are considered a sleep aid because airborne contaminants can cause health problems like congestion, headaches, stuffy noses, sneezing, and shortness of breath — all of which are proven to negatively affect sleep quality. This is especially true with people who have allergies, as well as those with asthma.
Additionally, most purifiers produce a subtle whirring sound that similar to the output of white noise machines, which are also used as sleep aids. White noise and other noise colors (such as pink) drown outside noise and allow people to fall asleep more easily. Some air purifiers come with a specialized ‘sleep’ setting, which is usually the lowest and quietest, and thus the most conducive to sleep.
Here are a few important factors to take into account when shopping for a new air purifier and comparing different brands and models:
- How much does the purifier cost? The price-point of an air purifier may range from $50 to more than $500, depending on the brand, model, and technology used. Pick a purifier that’s within your budget, and do not assume that a higher price-tag indicates higher quality.
- How big is the purifier? Some purifiers are tall and bulky but most are designed to take up minimal floor space. Your bedroom dimensions should be the deciding factor for the proper purifier size. Height may be a major consideration, as some purifiers measure more than 20 inches tall.
- How much does the purifier weigh? Although this varies significantly, most purifiers on the market weigh between 10 and 25 pounds. Be sure to test your bedroom floor before investing in a heavier model.
- Does the purifier use active or passive purification? There are benefits and downsides to both. Active purification does not feature replaceable parts and the purifiers tend to be quieter, but there are health risks associated with ionizer and UV technologies; additionally, this method is considered less effective because it transfers contaminants, rather than eliminating them. Passive purifiers completely destroy contaminants and are highly effective (for the most part), but the filters need to be replaced semi-regularly and the purifiers can be somewhat loud.
- What are the operating costs of the purifier? Ionizers and ozone purifiers don’t have parts that need to be replaced, so the operating costs for these models boil down to electric bills. Filter-based purifiers are costlier; expect to pay at least $150 per year in utilities and replacement parts, including the filter. Some filters cost as little as $10 to $20, while others are $100 or more.
- What kind of contaminants do you need to eliminate or transfer? As the table above shows, no purifier technology is effective at eliminating particles, bacteria, viruses, VOCs, and odors. Evaluate your home to determine the contaminants that matter most — and if need be, invest in a more expensive purifier that uses multiple technologies to target a wider range of contaminants.
- What is the coverage area? Most air purifiers are rated for effectiveness within certain room dimensions. Larger sizes can provide more coverage than smaller ones, and many models are available in multiple sizes. Measure the square footage of your bedroom before selecting a purifier; otherwise it might not be as effective as you would like.
- How many speed settings are included? Most purifiers sold today have multiple settings. Lower settings are typically best for sleeping time, and higher settings are better for times of the year when certain contaminants are high (such as pollen season).
- What are the timer settings? Most purifiers allow you to customize the timer, but some older models do not.
- Are there auto-adjustment settings? Some air purifiers are equipped with technology, to automatically adjust their settings based on the amount of particles detected in a certain room, and may also lower speed settings when there is no daylight.
- Does the purifier come with a warranty? Most purifiers come with some sort of warranty, which may last anywhere from one year to lifetime coverage.
There are other ways to cleanse the air in your bedroom other than (or in addition to) using a purifier. These include the following:
- Keep plants in your bedroom. This will improve oxygen levels in the room through natural purification.
- Never smoke in your bedroom. Purifiers are designed to reduce or eliminate particles from secondhand smoke, but smoking in your room may offset this. Also avoid burning candles, incense, and other smoke producers in the bedroom.
- Vacuum the room frequently. This will help keep particles out. If you use an ionizer or ozone purifier, this will be necessary to completely eliminate contaminants.
- Do not store VOC-emitting substances in the bedroom. Paints, adhesives, solvents, and other harmful substances should be kept in sheds, garages, or other areas that are separated from living quarters.
- Open windows in the bedroom when you are at home. This will greatly improve air circulation. However, this may not be possible during pollen season; clean the filters of your cooling unit in order to minimize particles in the air during high allergen periods.