SPM (SPM)

Suspended Particulate Matter (SPM), also called Total Suspended Particles (TSP), is the total mass concentration of all airborne particles in ambient air regardless of size — from sub-micron smoke up to 50-100 µm fugitive dust. SPM was the headline air-quality parameter in India's first National Ambient Air Quality Standards (1994) and remains a routine SPCB monitoring parameter in older consent conditions, even though current NAAQS (2009) emphasises the finer fractions PM10 and PM2.5 instead.

The measurement uses a High-Volume Sampler (HVS): ambient air is drawn at 1.1-1.7 m³/min through a pre-weighed glass-fibre filter for 8 or 24 hours, and the filter is re-weighed under controlled humidity and temperature. SPM concentration in µg/m³ is filter gain divided by total air volume sampled. The technique catches particles broadly above 0.1 µm, so SPM data correlates poorly with health endpoints (which respond to PM10/PM2.5) but well with visible nuisance dust, deposition on neighbouring rooftops, and visibility loss.

The 1994 NAAQS limits were 500 µg/m³ industrial / 200 µg/m³ residential for 24-hour average. After the 2009 revision, SPM was dropped from the federal NAAQS list but several states retained SPM in their consent conditions and CTE/CTO orders — particularly for industries with high coarse-dust emissions like cement, stone crushing, and recycling. Common contemporary in-consent SPM limits are 200 µg/m³ (industrial) and 100 µg/m³ (residential).

For recycling plants — tyre shredding, plastic granulation, e-waste dismantling, biomass pre-treatment — SPM is the parameter that determines fence-line nuisance complaints. Source controls are pragmatic: water sprays at shredder inlets and conveyor transfer points, total enclosure with a baghouse on dust hood capture, vehicle wheel washes at gate entries. The trade-off with finer-fraction PM10/PM2.5 standards is that controlling SPM with water sprays alone reduces coarse particles but barely touches the fine fraction; cyclones and ESPs are needed for the sub-10 µm population. Most consent conditions now stack SPM, PM10, and PM2.5 limits, so plant ventilation must handle all three.