Harsh but true.

What about household chemicals which are considered toxic or flammable , will these be considered a breach of lease?

I've had a few electricians look at the damage, and tell me over the phone that the reason for the damaged box is because ComEd when originally run wire underground to the home it did not leave enough "slack" and over the years with the home settling and the harsh winters the wire had pulled back from the home causing the box to be pulled along with it and cause the damage.

I guess the worst case scenario with the garage would be someone using noisy power tools or stinky chemicals.  

They manage the cleaning/balancing of the hot tub (we supply chemicals). 

I negotiate the relationships/contracts for one of the largest chemical producers in the world.

Those are some harsh words.

We were successful with a new chemical treatment. 

Ask them if they're okay with the smell of the orange natural cleaner (odds are these guys will also be afraid of chemicals). 

If you are in an area of harsh, cold , winter months make sure the end of your lease does not happen at the same time.It will be very hard to rent.So If you didn't like them and the lease was set to expire at an off peak market leasing time you might want to get rid of them now.