The annual recurrence of transboundary haze pollution1 from Indonesia is now part of Singaporeans’ lives. Yet, we still seem to be either in denial or ill- prepared given how severe its health and economic effects might be. At its peak this year, the Pollution Standard Index (PSI) in Singapore hit a high of 401 (a PSI of 300 and above is considered hazardous). Things could have been much worse: Singapore was fortunate to be spared the worst effects of the pollution, thanks to a change in wind direction; the Air Pollutant Index in Muar, a mere 165 km away, spiked at 746 (also considered hazardous at 300). That does not mean that Singapore is out of the woods yet. The National Environment Agency (NEA) has warned that the smoke may return if dry weather conditions persist in Sumatra and prevailing wind directions change. The causes of the haze pollution are complex and mitigation measures have not proven entirely effective so far. We must therefore also consider how we can best adapt to it and minimise its impact on us.

One adaptation measure is to take refuge indoors. But what statutory requirements exist for keeping the enclosed indoors safe from the haze pollution, and in particular the particulate pollutants that make up the dominant component of such pollution?


Performance standards

The Building  Control Act (Act),  through  the Building  Control Regulations, among other things, sets objectives and performance requirements for the design and construction of buildings.

The Act empowers the Building Control Authority to prescribe specifications, materials, designs or methods of construction which, if complied with, are deemed to comply with the relevant objective and performance requirement. Thus, the objective of “[protecting] people from loss of amenity due to lack of fresh air”2 is accompanied by the performance requirement to adequately provide ventilation in a building for its intended occupancy.3 This performance requirement is in turn deemed to be sufficiently complied with when the requirements of Singapore Standards 553:2009 - Code of Practice for Air- Conditioning and Mechanical Ventilation in Buildings (SS 553) are met.

Recommendations for air filtration of outdoor air for intakes in air-conditioned spaces are made in paragraph 7.5 of SS 553. Air filters should be installed such that no unfiltered air can bypass the filters and enter the air handling system. The Minimum Efficiency Reporting Value (MERV) of the primary filter for cleaning the recirculated air or mixed air should be MERV 5 or better. Where the quality of outdoor air is poor, such that the pollution standard index of outdoor air exceeds 100 based on PM10  over 24 hours, a second filter of 80% dust spot efficiency4 or better should be used for cleaning the recirculated air or mixed air or outdoor air of fine particles.

Filtration is also dealt with in Singapore Standards  554: 2009 Singapore Standards 554:2009 – Code of Practice for Indoor Air Quality for Air- Conditioned Buildings (SS 554). Paragraph of SS 554 provides that:-

“The quality of outdoor air introduced into the building should conform with the relevant USEPA or WHO ambient air quality standards adopted by NEA. Where this is not possible, appropriate air treatment should be considered…”

Paragraph recommends a “double-stage air filtration” consisting of:-

  1. Primary air filtration

Primary air filters having a Minimum Efficiency Reporting Value (MERV) rating of 6 or higher should be installed to protect the secondary air filters and air conditioning and mechanical ventilation (ACMV) system.

  1. Secondary air filtration

Secondary air filters having a MERV rating of 13 or higher should be installed to protect building occupants from airborne particulate matter (PM2.5)…

Furthermore, the building envelope design should minimise the introduction of pollutants due to infiltration from outside the structure.

SS 554 is not an “Approved Document” under the Act, but SS 553 and SS 554 are listed as “Approved Codes of Practice” under the Workplace Safety and Health (Approved Codes of Practice) Notification 2012. This means that while these Codes, not being subsidiary legislation, do not have the force of law, their compliance or otherwise may be relevant to proceedings for the purpose of proving the commission of an offence under the Workplace Safety and Health Act, such as the breach of duty by an occupier5 of a workplace6 “to take, so far as is reasonably practicable, such measures to ensure that the workplace… [is] safe and without risks to health to every person within those premises, whether or not the person is at work or is an employee of the occupier”.7 While not explicitly referred to in the Environmental Public Health Act, they would also be relevant for the purpose of considering whether the owner, lessee, or occupier of any building or part of a building to which the public has access has discharged his duty to “regularly clean and keep clean and in good repair the building or part thereof; and keep the building or part thereof free of such conditions as may endanger the lives or health of his employees, members of the public and other users thereof”.8

Outcome standards

SS 554 provides a “recommended” acceptable limit of concentration for PM10 indoors of 50 µg/m3 (8 hour mean) and “target” acceptable limit of 35 µg/m3 for PM2.5.

For air-conditioned offices however,  the Ministry of the Environment  and Water Resources’ recommended (non-statutory) maximum concentration for PM   (24 hour mean) is a more tolerant 150 IJg/m3 although it should be kept in mind that this recommendation is close to two decades old and predates SS 554 by more than 10 years.

For comparison, the World Health Organisation’s 24 hour mean guideline values for PM   and PM    are 50 µg/m3 and 25 µg/m3 respectively, although 10 2.5 the WHO clarifies that for most air pollutants, no threshold has been identified below which no damage to health is observed, and the standard setting process should achieve “the lowest concentrations possible in the context of local constraints, capabilities and public health priorities”.

Monitoring, maintenance, and audits

SS 553 provides for the regular inspection, maintenance and replacement of filters as required; the unit casing, air filters and passages of air handling units around coils must be checked for air leakage and rectified, if necessary, and filters in the air handling units and fan coil units must be cleaned or replaced as required.

Annex F of SS 554 recommends six-monthly inspections of the ACMV system, with each routine inspection covering 10% of the representative components, including the outdoor air intake and the air handling units. Full inspection of the affected component or part of the system serving the area complained about are recommended when problems are discovered during routine inspection or when complaints are made. Cleaning is recommended when the ACMV system discharges visible particulate into the occupied space or a contribution of airborne particles from the ACMV system into the indoor ambient air.

Finally, SS 554 recommends IAQ audits once every three years, including air sampling and obtaining feedback from building occupants once every three years for existing buildings, “in line with the risk assessment requirements under the Workplace Safety and Health (Risk Management) Regulations”.9

Concluding remarks

Considering the significant amount of time many of us spend in air- conditioned buildings, indoor air quality law is an area we too often take for a granted until something significant such as hazardous haze pollution prompts us to question whether the legal protection of our indoor air quality is adequate. Building owners and occupiers of workplace are under general statutory duties to ensure buildings protect occupants from loss of amenity due to a lack of fresh air; and workplaces are safe and free of conditions that endanger the health of occupants. In connection with these duties, they may also have to look to nonstatutory guidelines as to what constitutes good practice.10 In some cases, compliance with such guidelines may even be deemed to be conclusive evidence of the discharge of their duty, e.g. under
the Act. Conversely however, the noncompliance of these guidelines does not automatically amount to an offence.

In some cases however, compliance with these guidelines may not be sufficient, e.g. for the purpose of the Workplace Safety and Health Act and Environmental Public Health Act; after all, it is said that there is no known safe threshold for many air pollutants, including those produced by the haze. Hence, it is imperative for all stakeholders, including regulators, building owners and occupiers, to keep abreast of the evolving state of knowledge regarding the health risks posed by the presence of air pollutants indoors, and the best practices or reasonably practicable practices to minimise the health risks from exposure to these pollutants, taking into consideration that guidelines can become out of date or obsolete in the face of new circumstances including the regular recurrence of hazardous haze pollution outdoors.

In this regard, it is heartening to note that the government has commissioned a multi-agency team to review the indoor air quality of various premises to determine if the current Codes of Practice need to be further refined. This could result in the guidelines being updated, and provide greater certainty for all stakeholders. It may even result in the consolidation of all indoor air quality regulations into one statute or in giving these guidelines statutory force, even though present indications are that there is no intention to do so.