Here at The Chair Doctor we offer a chair cleaning service. Office chairs are often prone to coffee or other drinks being spilt on them in a busy office..
Some get dirty because of the environment they are in, basically through all chairs will get dirty over time. If the stains are treated early enough many are quite easy to remove.
For 10 or less chairs we will collect the chairs and take them to our factory, for more than 10 we offer an on-site service. We can also offer out of hours cleaning.
If the stains cannot be removed we also can quote to re-upholster the chairs. 
It should be noted that we recommend not using the chairs for12 hours after cleaning to ensure they dry thoroughly.