HEPA air purifier

Sources: Dyson, eBay 

• Adopts Dyson’s Air Multiplier™ technology that multiplies air flow by as much as 15 times. 
• 350° oscillation projects air around the whole room. 
• Has a quiet mode with dimmed LED lights during night. 
• Room coverage: 800 square feet (74.3 square meters)
• Dimensions (WxDxH): 9.8 x 9.8 x 29.4 inch (24.8 x 24.8 x 76.4 cm)
• Weight: 12.3 lb. (5.6kg)

Source: eBay

Pros

• The Dyson mobile APP helps track air quality in the room. 
• Combines heating, cooling and air purifying functions. 

Cons

• The mobile APP does not control heating. 
• Quite expensive.

Source: Cowaymega

• Four-stage filtration: Washable pre-filter, odor filter, true HEPA filter, and vital ionizer.
• Eco mode: Automatically stops when no air pollution is detected for 30 mins.
• Has three fan speeds. 
• Has a timer to pre-set 1, 4, or 8 hours of purifying.
• CADR: 

Dust: 246 cubic feet per minute (cfm)

Pollen: 240 cfm

Smoke: 233 cfm

• Room coverage: 361 square feet (33.5 square meters)
• Weight: 12.3 lb. (5.8 kg) 
• Dimensions (WxDxH):  16.8 x 18.3 x 9.6 inch (42.7 x 46.5 x 24.4 cm)

Source: eBay 

Pros

• Quiet, especially at lower speed. 
• Replacement filters are not expensive.
• Easy to operate.

Cons 

• Indicator light is so bright that you might want to cover it at night. 
• Not efficient when the room door is open. 
• works well for dust, but not for removing odor.

Source: Blueair

• Features three layers of filters: Fabric pre-filter that catches large particles, carbon filter that removes odors, and a main filter that traps airborne particles. 
• Works 360 degrees, so you can place it anywhere in your room.
• CADR: 

Pollen: 350 cfm

Dust: 350 cfm

Smoke: 350 cfm

• Noise: 32 dB when running at the lowest speed; 56 dB when at the highest speed. 
• Room coverage: 540 square feet (50.2 square meters)
• Dimensions (WxDxH): 13 x 13 x 20 inch (33 x 33 x 50.8 cm)
• Weight: 12.5 lb. (5.6kg) 
• Power consumption: 61 W

Source: eBay

Pros

• Simple to set up. 
• Relatively quiet depends on setting.
• Easy to tuck in a corner. 

Cons

• Filters are a bit pricey. 
• Awkward to move around as it has no casters or handles. 

Source: Dyson

• Features a backward airflow mode that purifies without cool airflow from the front.
• Delivers an estimated 77 gallons (291.5 liters) of clean air per second. 
• 20% quieter than its previous model. 
• Has a night mode for light sleepers.
• Room coverage: 800 square feet (74.3 square meters)
• Weight: 10.9 lb. (4.9 kg) 
• Dimensions (H x W x D): 41.5 x 8.1 x 4.6 inches (105.4 x 20.6  x 11.7 cm)

Sources: eBay, Breathe Quality

Pros

• Excellent in capturing smell and air-borne particles.
• Unique design.
• Combines cooling fan and air purifier. 

Cons

• A bit noisy. 
• Expensive.

Sources: Dyson, eBay

• Comes with an activated carbon filter and certified HEPA. 
• Captures up to 99.97% of dust and allergens with sizes as small as 0.3 microns.
• Monitors air quality on cellphone when the unit is linked to the Dyson APP. 
• Features a backward airflow mode that purifies air without cooling the room. 
• Has a sleep timer and night mode setting.
• Room coverage: 800 square feet (74.3 square meters)
• Weight: 18.3 lb. (8.3 kg)

Sources: eBay, PC Magazine

Pros

• The Dyson APP makes it easy to track air quality in the room. 
• The timer gives you more control as to when you want to use it. 
• Combines humidifying, cooling, and air purifying functions. 

Cons

• Expensive.
• When compared with many other products, the machine is relatively heavy.

Source: Cowaymega

• Three-stage filtration system that traps 99.99% of airborne particles and 99% of odor in a room.
• Room coverage: up to 1,560 square feet (144.9 square meters)
• CADR:

Smoke: 328 cfm

Dust: 328 cfm

Pollen: 400 cfm 

• Dimensions (WxDxH): 14.8 x 14.8 x 22.8 inch (37.6 x 37.6 x 57.9 cm)
• Weight: 24.7 lb. (11.2 kg)
• Power Consumption: 66 W

Sources: eBay, Business Insider

Pros

• Quiet.
• Wifi enabled.
• Filters only need to be replaced a year or so.

Cons

• Replacement filters are a little pricey.
• not effective in removing volatile organic compounds (VOCs).  

Source: Blueair

• Works 360 degrees, so you can place it anywhere in your room.
• Room coverage: 161 square feet (15 square meters) 
• CADR: 

Pollen: 120 cfm

Dust: 120 cfm

Smoke: 105 cfm

• Dimension (WxDxH): 8 x 8 x 16.7 inch (20.3 x 20.3 x 42.4 cm)
• Weight: 5.3 lb. (2.4kg)
• Power consumption: 1.5 – 10 W

Sources: eBay, Breathe Quality

Pros

• Quiet in operation.
• Light weight.

Cons

• The dust filter is not good enough.
• No Timer.

Source: Honeywell Store

• Claims to purify air up to 99.97% of airborne allergens and particles.
• Easy to use button settings
• Has 3 power setting (low/medium/high)
• Room coverage: 465 square feet (43.2 square meters)
• CADR:

Tobacco Smoke: 300 cfm

Dust: 320 cfm

Pollen: 300 cfm

• Dimensions: (WxDxH): 10.8 x 10.8 x 22.4 inch (27.5 x 27.5 x 56.8 cm) 
• Product Weight: 17 lb. (7.7 kg)

Sources: eBay, Consumer Analysis, Breathe Quality

Pros

• Processes more air more quickly than many others on the market. 

Cons

• Some users complained about a bad smell.