Selective Size Inlets
Total Suspended Particulate (TSP) Sampling
TSP is the suspended particle fraction in the atmosphere that includes particle sizes up to around 50µm diameter. Ecotech's TSP inlet has been designed to minimise the influence of wind speed and direction ensuring consistant sampling at all times.
Size Selective Inlets: Sampling at PM10 and PM2.5
Ambient air is drawn into the size-selective inlet at a constant volumetric flow-rate of 1.13m3/min (67.8m3/h) for both the PM10 and PM2.5 inlets. To achieve this, the HiVol 3000 uses a true volumetric flow-rate controller (via temperature and pressure compensation of a mass flow sensor.)
The size selective inlet (SSI) uses the principle of cascade impaction to seperate particulates based on size. The particles in the air are accelerated through multiple acceleration nozzles. Particles larger than the specified 2.5 or 10 µm cut-point gain sufficient momentum to cause impaction onto a greased collection shim where they are trapped. (The collection shim should be periodically cleaned and re-greased.) The PM10 or PM2.5 particles, however, are smaller and having less momentum, remain entrained in the air-flow and pass to the filter, where they are collected.
The SSI cut-point is affected by airstream velocity / flow-rate, acceleration nozzle diameter, and particle density, composition and shape.
The symmetrical design of the SSI overcomes the effect of wind direction and the inlet design makes the collection efficiency independent of wind speeds up to 36 kilometres per hour.