How to we disable an unused smoke detector

In our area, local codes made at least one CO detectors mandatory in all condos and rental units. I have had to replace dozens of standard smoke detectors with combo units in hard wired/battery back-up systems. Most every manufacturer makes a CO/Smoke unit that will plug in directly to the existing system. A hard wired replacement is far better than a stand alone battery operated unit, as it will alarm all units in the system if there is a problem.

Having the system monitored or not monitored makes absolutely no difference on how the system works inside the house. All monitored systems will work fine in the house even if the monitoring system is off.

Proper test methods depend on type, as there are different technologies employed depending on model. Some use a photo-sensitive element to "see" smoke, others use a radioactive element to detect products of combustion (even invisible ones), others "see" flames with an infrared detector and others detect heat.

You should test them exactly according to manufacturer's instructions and if they do not perform then replace them immediately. Like any other consumer product, you should deal with the seller and/or supplier and manufacturer for grievances related to defective products.

Exercise your right not to buy crap products and you will end up with reliable smoke/fire/CO detectors.