If you have one that is.

we've been in our house 2 1/2 years and I want to use ours. It's not horribly dirty or anything, but I know it needs a good cleaning. I know it takes awhile and stinks--is it safe while I'm pregnant? The smells won't do anything will they?
And, if you use yours, how often do you do it? Can you tell you did it by your electricity bill?