Managing Haze

Air Cleaning Devices

Air Cleaning Devices for Buildings

Air cleaning devices can be installed to regulate particulate levels in buildings with central air conditioning systems during a prolonged smoke haze period. Such devices include electrostatic precipitators and media filters.

Electrostatic precipitators operate by electrically charging dust particles as they pass a set of electrodes. The charged particles are then collected by charged collector plates (with an opposite charge) downstream of the charging electrodes. They have minimal effect on airflow.

Media filters are mats of fine fibres that are positioned perpendicular to the direction of airflow to intercept and trap particulate. They are available in a wide range of capture efficiencies. For smoke haze, filters manufactured for more efficient removal of fine particulate should be used.

Conventional medium- to high-efficiency media filters that can trap fine particulate are typically dense, and may hinder air flow if the fans are not designed to match them. Another type of medium-efficiency filter uses electrostatically-charged fibres to attract and retain fine particles. These filters are less dense and exert a lower resistance to air flow.

The capital and operating costs vary, depending on the type of air cleaning device selected, and the design of the air-conditioning system. Based on NEA's assessment, the overall annual cost of using such a device ranges from $2,000 to $10,000 for a floor area of 1,300 sqm. The costs are for an assumed haze period of three months in a year. Suppliers of these systems will be able to provide buyers with actual costs.

Portable Air Cleaners

Portable air cleaners are compact, standalone appliances designed to keep the particulate levels of an enclosed space low. In general, there are three main types of air cleaners available in the market.

They are:

a) Ionisers, which impart a negative charge to the particles that subsequently stick to surrounding surfaces or are filtered out;

b) Electronic air cleaners, which remove particles by electrostatic precipitation; and

c) High Efficiency Particulate Absolute (HEPA) air cleaners, which remove particles by mechanical filtration and diffusion.

Some portable air cleaners come with a combination of the above features. Several models of air cleaners can reduce the level of fine particles in a typical bedroom to an acceptable level during periods of smoke haze. 

The listed air cleaners will be able to provide adequate protection for a typical bedroom in a HDB flat with its doors and windows closed, with the occasional opening and closing of doors. Doors and windows should be opened occasionally – at least once a day – to ventilate the room.

For the purpose of smoke haze protection, it is useful to know the Clean Air Delivery Rate (CADR), which is the amount of clean air a device can produce for a room. A higher CADR indicates a greater ability to return clean air to the room. Knowing the CADR, as well as the size of the room where the air cleaner is to be installed, will help consumers to make an informed purchase. Buyers are advised to speak with device suppliers to obtain detailed product information to ensure the air cleaner they intend to purchase meet individual household needs.

NEA had published the Technical Advisory on Use of Air-Cleaning Technologies to Mitigate COVID-19 Aerosol Transmission Risk for guidance on the use of air cleaners amid the COVID-19 situation on 30 Aug 2021.  A new list of portable air cleaners effective against both COVID-19 virus and smoke-haze aerosols is expected to be published in Apr 2022.

The List of Portable Air Cleaners (for Smoke Haze) and Suppliers and the List of Suppliers of Air Cleaning Devices for Buildings are currently under review and new listing applications have been suspended until further notice.

Suppliers who wish to list their air cleaners under the new listing can submit the revised documents via the Online Feedback Form or the myENV mobile application according to the new requirement specifications.  The existing list of air cleaners for smoke haze will be removed by June 2022 with the replacement of the new listing.