As we move into summer we all feel the effects of humidity outside. It makes it feel so much hotter. You feel sluggish. The air just feels heavy.
Humidity can have that same effect when you are sampling dust using a photometer. It can overestimate your total mass measurement, making it seem heavier. Why? Photometers measure the light scattered by aerosol particles. When there is more moisture in the air, water hangs on to these particles and makes them appear larger. The instrument, in turn, gives you a higher mass concentration level. This can greatly affect the accuracy of your real-time measurements.
To help combat the effects of humidity, TSI developed a heated inlet conditioner for its DustTrak II and DustTrak DRX aerosol monitors. To test them, they went to Singapore and the coast of Australia. I volunteered tto go and observe. Sadly, I wasn’t invited.
Since I couldn’t be there in person, I’m going to have to rely on the application note TSI recently made available. To test urban pollution in Singapore, TSI took one DustTrak monitor and configured it with a heated inlet sample conditioner. It was set to condition incoming sample air to 30% Rh. The other DustTrak Monitor had no sample conditioning. Both instruments were programmed to run side-by-side for identical sample periods. The temperature in Singapore during the test averaged 83.6 degrees Fahrenheit. Relative humidity averaged 79.7%Rh. So hot. Really hot.
They found that the average change between the heated inlet conditioned measurements and the non-conditioned sample measurements was roughly 30%. That is a significant difference.
Now, these results have not been validated against federal reference methods and may not be indicative of all aerosols, but I think the takeaway is the that an inlet conditioner may substantially improve the accuracy of your real-time measurements.
For more information about the TSI DustTrak II and DustTrak DRX aerosol monitors.
RAECO-LIC LLC is the authorized TSI representative in the Midwest United States.