Re: How would I build a homemade 'spirometer' or measure lung capacity

The simple and classic device you seek requires the following 3 items:

1) A 1 liter graduated cylinder (which you should be able to borrow from 
your school's lab).  Also,
check to see if 1 liter is enough volume by running through the experiment 
that I describe below,
because I honestly don't remember what the human lung capacity is, off 
hand, but 1 liter sounds
like it should be enough, provided you're not measuring Andre' the Giant...

2) about 3 feet of common laboratory type rubber hose.  You'll need to have 
something you can
use as a disposable mouthpiece, for hygienical reasons - people will be 
blowing into the hose.  Try
going to one of them party shops - they sell a lot of bags of things people 
blow into to make noise
at partys, perhaps you can find something in there, or come up with 
something on your own.  My
mind is drawing a blank right now.

3) A large salad bowl or similar thing, perhaps bucket - full of water.

Fill the bowl or bucket with water.  Fill the graduated cylinder with 
water.  Put your hand over the
top of the cylinder, turn it upside down and stick it into the bowl or 
bucket of water upside down.
Some water will have leaked out and an air pocket will undoubtedly be at 
the top of the upside
down graduated cylinder.  Write down the volume of the air pocket by 
reading the graduated
cylinder.  Put one end of the hose into the cylinder and blow into the 
other end until your lungs are
evacuated.  Subtract the volume you wrote down before you started from the 
final volume after
your lungs were emptied.  That is your lung capacity.

This device should last forever.