This June 21st article from the Economist, “Hazed and Confused; Smog over Singapore” covers the recent pollution challenges in Singapore. The pollution is caused from fires used to clear lands in neighboring Indonesia – the smoke crosses the sea, making life miserable for the people of Singapore.
The Pollutant Standards Index (“PSI”) topped 401, with previous readings of 371 and 321. A 1997 score of 226 created concern. Over 200 is considered, “Very Unhealthy.”
As with any metric, the standards vary dramatically. Singapore still uses the PSI, which counts the micro-grams of material per cubic meter of air per day. The US has now moved on to the Air Quality Index (“AQI”) – which focuses on the size of the particulate in addition to their concentration levels. Respirable Suspended Particles (“RSP”) have diameters of 10 um or less. AQI focuses on Particulate Matter of 2.5 um (“PM2.5”) or smaller.
In the US filtration industry – PM2.5 would be picked up in a conventional filter depending on its MERV rating. The E3 channel covers particles from 3 – 10 um; the E2 channel from 1 – 3, and the E1 from 0.3 – 1 um. A MERV 16 filter would pick up at least 95% of the PM2.5 (> 95% E2 and E3 capture).
Filtration media could be used to make the facemasks more comfortable and to improve the indoor air quality for the people of Singapore looking to get out of the smoky outdoors. Providing that same efficiency of particulate remover with a lower pressure drop would reduce energy costs and likely allow for longer filter life.