Here are the things you need to consider.

1. If there is a fire potential here NOTHING you do can free you from liability if you knowingly install a screen that when in the down position could catch on fire.

2. So the question is, do you really want to be in the business of trying to make your automation system prevent a fire because the Client/designer is choosing to do something dangerous and you want to please them or make a sale, versus saying "I'm sorry, this is dangerous, if you are going to put a fireplace here, a screen cannot be put here".

3. In some ways you are INCREASING your liability by trying to design a fail safe. Now it is YOUR FAULT if something goes wrong. You'd need to consult an attorney but in some ways you might be much better off telling the customer this is unsafe, I'll install the screen based on the understanding that you don't ever actually use your fireplace.

4. A liability waiver does not stop you from being held liable if you do something negligent. Think about it this way. If I ask an electrician to install an outlet on the wall above my tub so I can plug my razor in when I'm in the tub, and promise I'll never use it when water is in the tub, which seems the correct path?

a. The electrician tells me that's against code, is unsafe, and he can't do it.
b. The electrician does it, and tries to figure out how to put a sensor in the sub to detect water and make sure power to the outlet gets killed if I'm in the tub, so I don't get killed.

If he does b, what do you think is going to happen to him if his water sensor doesn't work?

The purpose of home automation systems is to increase ease of use and enhance safety. NOT fix dangerous systems/stupid decisions by the Client or interior designer.

[Link: controlworks.com]