The QCM is quite a simple machine, and extremely robust (go read about it in wiki). It uses the impact of mass on the oscillation of a piece of quarts to measure the weight of an object down to the billionth of a gram or better. We were taking measurements of our breath at GOSH while a really loud band was playing in the same room - yeah, it's awesome :)
Anyway, it gets used for a wide range of interesting things in labs, but because of it's robustness and the relative simplicity of the actual measurement... but after talking with Macro I think there's unexplored applications in the field. Imagine this as the simplest possible example:
1) Let's say I put a piece of active carbon (which absorbs everything out of the air) on the QCM, and put in in a room and took a reading every minute. If there were periods of lots of dust or soot in that room, I would see the rate of increase in mass of the active carbon go up during those periods. I could even quantify in pretty exact terms the amount of particulate in the air based on the rate of accumulation.
2) Ok - so that's cool but very non-specific. To get a bit (only a bit) more fancy, what if I had a piece of functionalized active carbon (or some other polymer or something), where the functionalized component only absorbed my pollutant of interest... So the rate of mass gain was proportional to the amount of that specific material in the air. In this case, depending on the amount of pollutant and rate of absorption, one could imagine having this out in the field for quite some time before it began to saturate my functionalized material (this is calculatable).
Again, what's cool is this is relatively cheap, relatively simple technology which could be designed to hold up in the field, and is kind of infinitely expandable to a variety of different possible pollutants based on the method.
So that's it - what do you guys think?