Commentary: Why staying indoors may not be enough when haze hits

Commentary: Why staying indoors may not be enough when haze hits When sheltering from haze in indoor spaces, air filtration, cooling and ventilation need to be considered together, says SUSS’ Zuraimi Mohamed Sultan. SINGAPORE: Singapore recently saw its worst haze episode since 2015, logging 18 consecutive days of unhealthy air from Oct 5 to 22. The National Environment Agency (NEA) expects that wet conditions should suppress hazy conditions until Thursday (Oct 29). What have we learnt from coping with the past few smoke-filled weeks, and are we prepared for another haze episode? To reduce exposure to haze particles, the NEA recommends that individuals stay indoors and close windows and doors. However, doing so can sometimes involve trade-offs between health and comfort. Consider an older person living in a flat without air-conditioning. Closing windows can make the home warmer and stuffier, while reopening them during haze allows particles back inside. Singapore has set up community haze shelters which are available to the public when the 24-hour Pollutant Standards Index (PSI) exceeds 200. Healthcare institutions are prepared to close windows and use air purifiers and portable air coolers where appropriate. These efforts help protect vulnerable groups. However, the ability to maintain a comfortable indoor environment with reduced haze exposure still depends on housing circumstances, financial resources, mobility and available support. Advice to stay indoors must therefore be accompanied by practical measures that enable them to do so comfortably and with reduced haze exposure. CLOSING WINDOWS CHANGES THE INDOOR ENVIRONMENT Heat, carbon dioxide and other pollutants may accumulate in enclosed rooms, particularly when occupancy is high. Reopening windows when outdoor air quality improves can help restore ventilation. The challenge arises when haze persists, especially in spaces that rely on natural ventilation to maintain acceptable indoor conditions. Indoor protection depends on ventilation arrangements, available equipment and occupants’ needs within each home. Residents with limited mobility may have difficulty adjusting windows, operating equipment or moving to a more suitable space. Similar considerations apply to naturally ventilated nursing homes and hospital wards, as well as schools and childcare centres. Existing haze preparedness measures provide important protection, but their effectiveness should be assessed under actual occupancy and operating conditions to ensure that particle exposure, ventilation and thermal comfort are adequately managed. COOLING, FILTRATION AND VENTILATION SERVE DIFFERENT PURPOSES Fans can improve thermal comfort by increasing air movement across occupants, particularly in closed indoor spaces without air-conditioning. However, ordinary fans do not reduce room temperature, remove haze particles or introduce fresh air when they simply recirculate indoor air. Similarly, while air-conditioning provides cooling, its presence alone does not ensure adequate particle filtration or ventilation. Air purifiers can reduce indoor particle concentrations, provided their capacity is appropriate for the room. Effective performance also requires suitable placement, correct operation and regular maintenance. Cooling, ventilation and air filtration need to be considered together. A comfortably cooled room may still have inadequate ventilation, while a room with effective particle filtration may become excessively warm. Haze preparedness should therefore address particle exposure, ventilation and thermal comfort as complementary aspects of indoor protection. In shared buildings, facilities managers can assess existing systems and establish procedures for responding to changing conditions. Monitoring indoor particles, temperature and carbon dioxide – the latter as one indicator of ventilation adequacy – can support decisions alongside information on occupancy and occupants’ needs. In healthcare facilities, these arrangements must also be coordinated with clinical and infection-control requirements. Households may lack the equipment or expertise available to institutions. Purchasing an air purifier involves an initial expense, followed by the costs of electricity and replacing filters. For residents with limited income, these can compete with essential spending. Targeted equipment loans or subsidies could help vulnerable households establish one room with reduced particle exposure and adequate comfort. Support should extend beyond equipment provision to include maintenance. Practical assistance matters as much as equipment. Volunteers or community partners could help older residents operate devices and position them appropriately. Community haze shelters provide another avenue for protection. Their accessibility depends on residents knowing their locations and opening hours, being able to travel there, and having arrangements that allow them to remain for the required period. OUTDOOR WORKERS NEED SOMEWHERE SUITABLE TO RECOVER The built environment also has an important role in protecting people who work outdoors, such as construction workers and delivery riders. Depending on the air quality, the Ministry of Manpower’s (MOM) guidelines advise employers to reduce, minimise or avoid strenuous outdoor work, and mitigate risks through measures like scheduling indoor rest breaks and deferring non-essential tasks. More could be done to ensure outdoor workers have suitable places to rest. Employers could ensure there are designated indoor spaces where workers can shelter during periods of poor air quality. This would require arrangements to pause or reschedule outdoor tasks, together with access to spaces with particle filtration, ventilation and thermal comfort. For delivery riders, platforms could work with building owners and businesses to identify accessible indoor rest spaces. Delivery schedules and incentive arrangements should enable riders to take protective breaks without undue pressure to return outdoors. N95 masks remain important where respiratory protection is indicated. However, their use may increase breathing effort and cause discomfort for some workers. Suitable indoor spaces could support breaks from outdoor exposure and allow temporary mask removal. Employers and platforms should therefore coordinate work schedules, rest facilities and operational expectations to make sheltering during haze peaks a feasible protective measure. Singapore’s advisories and institutional measures provide essential support. Building on them means examining whether the places where people shelter are appropriate. For an older resident, that may mean assistance with filtration and comfort at home. For a school or care facility, it may mean checking how equipment performs in an occupied room. For an outdoor worker, it may mean access to an indoor rest space. Advice to stay indoors becomes more effective when people can access an environment that reduces haze exposure without compromising comfort or ventilation. Dr Zuraimi Mohamed Sultan is Head of Programme, Facilities Management at the School of Science and Technology, Singapore University of Social Sciences.