Directional Dust Gauges also known as CERL Gauges
This instrument is designed for dust monitoring for flux, usually quoted as mg/sq m/day
There are four collectors spaced at 90 ° intervals around the stand. Each collector is a vertical plastic cylinder with an internal diameter of about 75mm and with a rectangular slot 340mm x 45mm, so its area is 0.0153 m2. The tube diameter is of no relevance to the calculation.
If the collecting head under consideration collects W mg in D days, then the flux is given by:
Flux = W/0.0153/D or [65.36*W]/D mg/ m2/day
For example, if 200mg were collected in 32 days, the result would be:
Flux = [65.36*200]/32 = 408.5 mg/ m2/day
This calculation needs to be repeated for the remaining three heads
There is a popular misconception that these gauges measure dust deposition whereas they attempt to measure dust flux. This flux is the vector product of airborne particle concentration (mass per unit volume) and the horizontal component of the windspeed (velocity) and thus has the units of mass per unit area per unit time. It is unfortunate that the units of dust flux are therefore the same as those of dust deposition, adding to the confusion. It is NOT possible to convert readings obtained by the directional gauge into deposition rates as the calculation would require knowledge of particle size, particle concentration and wind velocity components, most of which are not known. Adding the flux from the four collecting heads does not magically convert this directional gauge into a deposit gauge as some practitioners imagine.
Contents of kit
Main assembly consisting of quadruple collectors on plastic-coated steel stand with heavy-duty base plate
4 x 1000ml HDPE collecting bottles with internal seal
1 x 600ml wash bottle
4 spare collecting bottles
Calibration data
Overall height 1.6m, weight approx 14kg
Benefits
Collecting heads and stand manufactured in accordance with former BS1747Pt5 for consistent performance
Collecting heads made from heavy gauge black uPVC to reduce vibration and improve dimensional stability
Robust collecting bottles of white HDPE with red HDPE attachment caps
Optional squeegee to facilitate removal of dust from collecting heads
