I am very sorry madam, but I fear that my equipment may be damaged if I use it to clean your carpet.
OR
I am afraid that I need to get my innoculations up to date before I attempt a job like this.
OR
Have you considered tarmacing your living room ?
OR
My machines JUST broken down, I will give you a bell when its fixed
OR
I am a member of the R S P C A , I couldnt kill a living thing(s)