Indoor Air Quality guidelines

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Indoor Air Quality Pyramid
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Biz in Category 1:
Offices & shops with windows access/open air & low human traffic
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Biz in Category 2:
Offices & shops with individual split air-cond system & low human traffic

Biz in Category 3:
Commercial office building, shopping mall, hotel, convention center, concert hall, cinema, air-conditioned factory with centralized air-cond system & high human traffic

Air Cleaning Technologies used to reduce air borne contaminants including viruses in enclosed environment:

  1. Mechanical filtration
  2. Portable air filter device
  3. Ultraviolet Germicidal Irradiation (UVGI)
  4. Electronic air cleaners
  5. Chemical spray for air cleaning
  6. Maintenance of air-cleaning devices

Mechanical Filtration:

  1. Improving ventilation is the primary measure.
  2. Air cleaning technologies can be used as a supplementary strategy esp in spaces where ventilation cannot be easily improved (i.e. no doors/windows, clean room or dust free requirement, semi-conductor factory, data center,…etc) or in spaces with high risk activities.
  3. Mechanical filtration (installation of high efficiency filters e.g. MERV14 standard) & UVGI is recommended by American Society for Heating Refrigeration Air-Conditioning Engineers (ASHRAE) & NEA Spore to install in commercial air-cond system to treat recirculated air. Pls consult a qualified air-cond engineer with experience in commercial HVAC system.

Portable Air Filter Devices:

  1. In spaces where ventilation cannot be easily improved and/or high risk activities are on-going, portable air-filtering devices may be considered as an interim measure.
  2. Portable air-filtering devices equipped with high efficiency HEPA filter (which is 99.97% efficient at capturing particles 0.3 micron size. Coranavirus is about 0.1 micron size and is likely exhaled in larger respiratory droplets.
  3. The effectiveness of a portable air-filtering device depends on both the airflow rate (cfm) and the filter efficiency for eg HEPA filter.
  4. Some portable air-filtering devices may contain additional function i.e. ionizer (which is not well established according to NEA, Spore).


  1. ASHRAE has recommended a minimum of UV-C (254 nm wave length) for 99% inactivation of Coronavirus.
  2. For safety guidelines for use of UVGI Devices in commercial or industrial air-cond system, pls consult a qualified air-cond. engineer with experience in commercial HVAC system.
  3. NEA, Spore highlighted that UV radiation should only be executed by trained professionals for specific purposes for eg, in hospitals and laboratories. As UV-C radiation can cause injury to the skin and eye, NEA, Spore does not recommend the household use of sterilisers that use UV-C radiation for disinfection. This is because some devices marketed for home use lack safety features.

Electronic Air Cleaners:

  1. Electronic air cleaners use technologies such as ionizer, negative-ion generator, photocatalytic oxidation and non-thermal plasmas to generate reactive ions or reactive oxygen.
  2. According to NEA Spore, the efficacy of most Electronic Air Cleaners in inactivating virus is not supported by consistently robust scientific evidence. Moreover, the disinfection efficacy of such product in real world setting as well as potential unintended side effects are not adequately documented.
  3. Electronic air cleaners may generate ozone which could have potential health effects (e.g. respiratory or skin irritation).

Chemical Spray for air cleaning:

  1. Prepare disinfectant solution according to KKM or NEA Spore approved list of disinfectant effective against Coronavirus.
  2. Sanitize high exposure area 3 times daily.
  3. Avoid using spray to apply disinfectant on potentially highly contaminated areas (such as toilet bowl) as it may create splashes which can further spread the virus.

Maintenance of Air-cleaning devices:

  1. Air filters and UV lamps should be replaced according to manufacturers’ recommendation.
  2. Chemical cleaning of air-cond

Comparison of Portable Air Filter and Electronic Air Cleaner

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