|MadSci Network: Microbiology|
Sounds like a very interesting experiment. I am guessing that you don't have a particular gas that you are looking to measure. I would suggest that you measure atmospheric carbon dioxide in a closed chamber.
Mold produces carbon dioxide as a byproduct of metabolism. So, the more the mold is growing and consuming the food you provide, the more carbon dioxide should be produced. However, there may be other microbes there as well that also contribute some carbon dioxide. If you use a food that the major type of microbial growth to expect will be fungal you should be OK. This would be something like bread that has a fairly low moisture content which will keep most bacteria from growing.
To do this, I would use a fairly large container that you can seal. The
large air space will allow enough oxygen to be present for the mold to grow
and prevent the rapid build up of too much carbon dioxide. You should
be able to get quite a bit of mold growth under these conditions. You will
also have to use a carbon dioxide detector. Several of these are
commercially available. An example can be seen at this website:
I hope that helps.
Try the links in the MadSci Library for more information on Microbiology.