OK so I reread the post and I tend to agree with some of the other posters that the Landlord should be supplying the fire extinguisher. Originally I was looking at this as something new being added, but, this has already been a part of the rental. If an item like this extinguisher, is being replaced or updated due to ordinance I think that's on the Landlord, to make sure the property is up to code and fulfills his/her insurance liability. This would not require any Change in the Rental Agreement, just should be a part of the house rules. I have multifamily units (12), I provide the fire extinguishers, yearly inspection and any replacements. Thanks for bringing my first answer to my attention.