Purifier

Parameters

Air flow rate

  • Clean air delivery rate (CADR) - amount of clean air coming out of the air purifier on the highest fan speed.
    • Definition: Volume/Time of air in a 1,008-cubic-foot (28.5 m3) room that has had all the particles of a given size distribution removed from the air, over and above the rate at which the particles are naturally falling out of the air.
    • Example: 138 CFM (smoke), 161 CFM (dust), 219 CFM (pollen) for Coway Airmega 150
  • Common units: CFM = cubic feet per minute. cubic meters per hour. liters per sec.

Air changes

  • If outside air is entering with new allergens/ pollutants - purifier has to do more work - so one needs to account for air changes per hour in determining target CADR.
  • Air flow should be appropriate for the size room that needs to be treated, and capable of generating 8 or more air changes per hour in a room of that size (decreasing particle levels by 90% or more—the correct target in medical situations).
  • Air cleaners are usually advertised with the room size for which they are recommended. Keep in mind, however, that this recommendation is based on the unit’s ability to provide five or six air-changes per hour in a room of that size, a rate that is sufficient to decrease particle levels in the room by about 70%. Remember also that these figures are based on using the machine at its highest speed, which is also its noisiest speed.

Example requirement

  • 12 x 10ft room (120 sqft = 11.15 sqmt) with 10ft ceiling - (1200 cft = 34 m^3).
    • 20 CFM or 34 m^3/h for 1 air change per hour.
    • 100 CFM or 170 m^3/h or 472.2 L/s for 5 air changes per hour.
    • 160 CFM or 272 m^3/h or 755.6 liters/ sec for 8 air changes per hour.

Filter cleanliness

  • Clean filter => more air flow (6 times more in case of Conway Airmega 150 per their video).

Filters

HEPA

  • HEPA (High Efficiency Particulate Air) filter removes 99.97% of all particles as small as 0.3 microns from the air that passes through it.
  • most of the air purifiers sold in the market (price no bar!) come with H11 or H12 or in some cases H13 HEPAs and are also smaller.
  • H14 unit - better filtration rates, especially for the finest particles. It also has better filter life.

Carbon

Noise

  • For less sound (and longer motor life) you may want to have a unit capable of effective cleaning when running at less than its maximum blower speed, especially when you are in the room.

Air vent placement

  • some popular air cleaners blow the cleaned air downwards onto the floor. This has been shown to blow allergens from the floor (especially if it is carpeted) into the air, thus negating the benefit of the filter.
  • ozone
    • work primarily by generating charged particles (ions), which in turn cause other airborne particles, including allergens, to stick to solid surfaces. However, such ionizers also release into the air ozone, a form of oxygen that can worsen allergy and asthma symptoms.
    • HEPA type air cleaners that generate a minute amount of ozone confined to the machine increase the effectiveness of the HEPA filter, do not release ozone into the air of the room, and are safe.

Filter vendors

  • H13 HEPAs - ilovecleanair

Purifier Vendors

  • Sharp - Japan design, made in Thailand.
    • FP-F40E-W -details below
    • FP-J40M-W - CADR - 240 m³/hr. 16,590 on Croma.
  • Coway - Korean design. Likely Chinese make.
    • Coway 150 Mega has good Indian reviews. Supposedly good customer service. Cheaper by 4k in USA. Air might get sucked in seams - so might need to down-rate performance by 10%.
  • Glen - Chinese make.
    • Glen 6033 - 230 m³/h. 7k. HEPA filter at 700.
  • Panasonic
    • F-PBJ30ARD
      • Replacement filter - 4500rs
  • Honeywell - China make
    • HAC25M1201W 250 cu m/hr
  • Dyson - Malaysia expensive.
  • Eureka Forbes - Chinese
  • Phillips - China
  • Kent - ?
    • Supposedly poor service.
  • SmartAir Squair
    • (CADR) of 315 m3/hr. 6W 23db (low setting).
    • Carbon and HEPA filters

Sharp FP-F40E-W

Specs

  • Noise: On medium speed, from 7-8ft you almost cannot hear it at all
  • Power consumption on High is 31w (ceiling fan is 65W). On Medium it’s consumes just 12w. sleep mode is a mere 3.7-5.9w!
  • CADR - 240 m³/hr. 10-11k online.

Filters

  • PM10 pre-filter can be used life-long. Carbon and HEPA - 2 years life.
  • Filter FZ-F40SFE - 5k on Amazon.
    • High grade H14 HEPA filter.
  • Clean the deodorising filter at least once a month and chuck it out after 2-3 months, max! replace it with a third party PM2.5 fine filter like what naso, 3m, Smartair etc offer. They usually cost about ₹400/pair.