ASSESSMENT OF FILTER EFFICIENCY IN THE FAN FILTER UNIT FOR HAZE INCIDENT

Abstract

The episode of periodic haze in Singapore is no longer foreign to the country. The issue of breathable air caught public attention in 2013, when trans-boundary haze hit record high PSI of 400 points, otherwise described as hazardous (NEA, 2014). It is then recognized that although purifiers have been developed, problems with indoor air quality still arise because the machines purify and recycle air – there is no fresh air intake into the room. Furthermore, the purifiers are usually expensive and one purifier is insufficient and cost inefficient in serving larger spaces such as classrooms. A low cost, low maintenance fan filter unit is thus developed as a long term solution. The FFU consist of two parts – the fan and the filter media. The primary goal of the invention is to remove particulate matter from the air drawn inwards, thus filter efficiency becomes the utmost important variable in the choice of filter. A laboratory rig test was set to test 4 types of clean filters of different standard MERV ratings (Unrated, MERV11, MERV13 and MERV16). The filters were compared relatively for their efficiency behavior across the removal of PM1, PM2.5 and PM10 particles. It was observed that the MERV13 filter would be the most suitable and recommended filter efficient in dust removal and cost as a part of the low cost FFU. The similar set up was used to test loaded version of the 4 filter types to verify manufacturer claims that filter efficiency rises with duration of use. It was found that both the unrated and MERV11 filters agreed to the statement which MERV13 and MERV16 filter did not. The information provided in this paper serves as a guide to help users make more informed decisions about the choices of filter for the low air velocity FFU.