KUALA LUMPUR, Oct. 26 -- Keeping windows and doors shut during haze can help limit polluted air entering homes, but it may not be enough to protect occupants from fine particles that seep indoors, two indoor air quality specialists said.

Syida Nasri, Airscan's head of indoor air quality and a Department of Occupational Safety and Health-accredited indoor air quality assessor, said fine particulate matter measuring 2.5 micrometres or less (PM2.5) could enter homes through gaps around windows, doors and other openings, even when they were kept closed.

"Merely staying indoors isn't enough to protect against the haze," she said.

PM2.5 is of particular concern because the particles are small enough to penetrate deep into the lungs and, unli...