CleanForce CP-Rainbow: I was impressed by the performance of this unit. It was the fastest air purifier at removing particles at high fan setting, removing all smoke particles in just 1 minute and 45 seconds, which is just incredible. It comes with app control and voice command, an HD LED display for air quality monitoring and color-coded indicators. It offers just a hair fewer features than our winner for best air purifiers for large spaces, but it's considerably more expensive, which is why it's not topping the list. Independently tested and AHAM Verifide to circulate and filter room air up to 4.8 x per hour in a 155 sq. ft room. 2 (medium room air purifier) The Honeywell HPA100 Air Purifier has earned the ENERGY STAR label by meeting strict energy efficient guidelines set by the U.S. EPA. Room air purifiers have demonstrated the potential for improving air quality and providing health benefits. EPA does not endorse manufacturer claims regarding the degree to which a specific product will produce healthier indoor air.

HEPA Filtration: this home air purifier helps capture up to 99.97% of the following microscopic airborne allergens and particles: dust, pollen, pet dander, dust mite debris and smoke. 1 Medify MA-25: The performance didn't justify the price with this unit. It struggled in our particle removal test, and was the loudest of the small-sized air purifiers we tested. Good air quality is particularly hard to maintain in large and open spaces. For this category, the most consistent unit was the Kenmore Smart 2000e. At low, it was able to purify the air in our test chamber in approximately 6.25 minutes, the fastest of the bunch. At high, it came in second, reaching the finish line in only 2.5 minutes. In truth, it's a combination of anthropogenic (human-generated) and naturally occurring particles. The former is composed mostly of urban, industrial and automotive emissions of hydrocarbons, nitrogen oxides and combustion byproducts, and the latter is mostly represented by smoke from forest fires, sulfates, soot and matter from volcanic activity around the globe. We are, at all times, breathing in a mixture of it all. Cutting your pre-filter is easy. Simply remove the pre-filter from its box and use the provided cutting template. Following the cutting template will ensure your pre-filter is the correct size for its untended unit. Once you've finished cutting, you'll want to secure the pre-filter under the clips located on the rear of the air purifier's grille. Why are there two filters in my air purifier? What are the differences?Some air purifiers, including the Coway Airmega 400, are designed to purify rooms as large as 1,500 square feet. David Priest/CNET Budget

Note: These replacement intervals are intended as guidelines only. Performance of any filter media is dependent upon the concentration of contaminants going through the system. High concentrations of contaminants such as dust, pet dander, and smoke will reduce the useful performance of the filters. HEPA Filtration: This home air purifier helps capture up to 99.97% of the following microscopic airborne allergens and particles: dust, pollen, pet dander, dust mite debris and smoke. 1 When considering your budget for an air purifier, you might also want to consider the cost of replacing the filter roughly every six months. Types of air purifier A Swiss manufacturer we’d not come across before, Stadler Form launched their first product, the odd-looking Fred humidifier, in 1998 and now produce high-quality fans, heaters, dehumidifiers and air purifiers. Our favourite is this one, Roger Little (there’s also a Roger Big for 104m 2 rooms and plain old Roger for 66m 2 rooms). Independently tested and AHAM Verifide to circulate and filter room air up to 4.8 x per hour in a 500 sq. ft. room. 2 (extra large room air purifier)

The Telegraph does not yet have a laboratory for accurately measuring air pollution (we’re working on it), so instead we relied on the advice of buyers at large department stores, who deal with the full range of air purifiers and know the pros and cons of each one. We were looking for the best filtration power at the best price, but also took into account looks, reliability, fan and air cooling functions and the reputations of the manufacturers. In addition, many will include active carbon filters to remove traffic fumes, cigarette smoke and volatile organic compounds (VOCs) from people, animals, plants and products in our house. The carbon is treated to have an extremely high surface area – it’s ultra-porous – attracting small particles to it and trapping them. Active carbon filters are known for removing bad smells. Where to place an air purifier

The Honeywell InSight™ HPA5300 HEPA Air Purifier earned the ENERGY STAR label by meeting strict energy efficient guidelines set by the U.S. EPA. Room air purifiers have demonstrated the potential for improving air quality and providing health benefits. EPA does not endorse manufacturer claims regarding the degree to which a specific product will produce healthier indoor air. At just 18dB on its lowest setting, the Blue 3210 is technically quieter than a whisper. It’s certainly the quietest we tested as well as one of the most efficient, using about as much energy as an LED lightbulb. This portable air purifier uses an activated carbon pre-filter that helps capture large airborne particles and reduce odors and VOCs.HEPA air purifiers: Standing for "high efficiency particulate air," air purifiers with HEPA technology use a fiberglass filter that traps particles of a certain size out of the air. The CADR rate measures how much air is filtered in cubic metres per hour (m 3ph) of clean, purified air produced. The higher the CADR rating, the cleaner the air in the room will become. As a rule, if the square root of the CADR rating matches the floor area of the room – eg 625m 3ph in a 25m 2 room – it is an excellent air purifier. Three-quarters is good and half is acceptable. You may see CADR measured in cubic feet per hour on American devices, but the maths is the same. On top of that, the Kenmore Smart 2300e was one of the most efficient large-size air purifiers we tested and would add less to your monthly energy bill than similar-size units like the Coway Airmega 400s or the EnviroKlenz Air System Plus. It wasn’t unreasonably loud, either, keeping the fan noise below 40 decibels at low and medium settings and topping out at 50.6 decibels at its highest setting. That’s comparable to the noise generated by rainfall. This air purifier for allergies is AHAM (Association of Home Appliance Manufacturers) Verifide meaning that it has been independently tested to ensure its efficiency in reducing smoke, dust and pollen in the suggested room size. (extra large room air purifier) The AHAM assigns a CADR (Clean Air Delivery Rate) Rating that measures the volume of filtered air delivered by an air cleaner. The Honeywell HPA5300 InSight™ HEPA Air Purifier received the following CADR Rating: Cleaning Levels (Microscopic Particles, General Clean, Pollen and Turbo) make this an excellent air purifier for allergies