I recently consulted with Reb Wosner about a factory that I was hired to take care of the mezuzos. There were hundreds of doors, and the factory had a very strong chemical smell (the kind of smell that makes me never want to use anything that has chemicals in it again). Here are the guidelines that he gave me:
1. All offices in use require mezuzos.
2. Office hallways need mezuzos.
3. Storage rooms need mezuzos.
4. Doors to the outside need mezuzos.
5. Rooms where Jewish workers don’t regularly go do not require mezuzos.
6. Rooms with bad chemical smells don’t need mezuzos.
In this particular factory, this eliminated many of the doors. In all, I put up about ninety mezuzos.