Is this a reasonable request to Tenant?

[Marci Stein]

My (excellent) tenant , and 2 sm dogs have  been in the house five years without any issues .
 I asked her to get the heating and clothes dryer  vents   professionally cleaned ($300?)

She said she will do it herself, but  that is not possible to do thoroughly . 

Do you ask your tenants to pay to keep the vents clean ? 
i’m about to write up a new lease and would like to include this- is it fair?

Thanks very much  !