Frequently Asked Questions
Indoor Air Quality
Particulate Matters (PM) are mix of very small solid particles/liquid droplets in the air, varying in sizes. They are one of the most dangerous air pollutants and can cause death, severe respiratory diseases, asthma, lung cancer, etc.
ppm: parts per million
ppb: parts per billion
µg/m3: is micrograms of gaseous pollutant per cubic meter of ambient air
mg/m3: one milligram per cubic meter
µg versus mg
A milligram is generally abbreviated as mg.
One microgram is one millionth of a gram and one thousandth of a milligram. It is usually abbreviated as mcg or ug. Mcg and ug are the same
At 760 mmHg and 20 oC, 1ppm = 1.165 mg/m3 and 1 mg/m3 = 0.858 ppm;
at 25 oC, 1 ppm = 1.145 mg/m3 and 1 mg/m3 = 0.873 ppm.
Indoor Air Purifiers
- Clean Air Delivery Rate (CADR) at a medium spead, where the noise level is acceptable and not high – it should be able to provide for atleast 2 air changes in one hour.
- HEPA filter quality: A good quality hepa filter is an important factor to consider. A true Hepa filter should be of H12 or H13 grade.
- Carbon filter: A good quality carbon filter weighing 500 grams or above.
- Pre-filter: a good washable pre-filter to take care of larger particles.
- Noise levels: Below 50 dB, at medium speed, should be acceptable.
- Indicator for filter change.
- Air quality indicator (PM2.5 / PM 10, CO2, etc).
For any air purifier to be effective, it has to move the air. As such, there is no way to do this silently. However, with most air purifiers, there is a noise level setting that can be adjusted based on preference.