#433: Sootometer

When I was a child, the Radiometer was probably the first device that I was aware of which the adults in my family couldn’t explain convincingly. I’m still short of a how-it-works theory which satisfies me, but it forms the basis of today’s invention.

I noticed that the vanes of the radiometer which I was given 30 years ago had recently stopped moving. Wiping a small area of dust from the top caused them suddenly to restart. It occurred to me that here we have a system capable of measuring more than household dust. It is a potential, low cost monitor of airborne pollution.


This is a matter of concern for me because I regularly spend time working by the window of a city centre office which is visibly speckled with sooty particles. Using a suitably calibrated radiometer, I can now be aware quantitatively of the ambient level of atmospheric particulates inside the building -when the vanes become immobile, it’s time to evacuate or activate the expelair.

This simple system incorporates a small fan, to accelerate the deposition of specks on the glass, and a selection of smoked glass filters to boost the sensitivity to their density. This could be supplied to urban schools, for example, in order to protect children from pollution.

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