Recently, I went into an apartment and the tenant had disconnected the smoke detector. He is a smoker and the alarm goes off whenever anybody smokes. He did not notify me and if the apartment caught fire this could have been a major safety/liability issue. This is a major issue for ALL landlords! Tenants must keep smoke detectors connected and landlords must regularly check for compliance and to see if the detectors are working properly. If you are a landlord perhaps add into your lease a fine or consequence for tenants disconnecting detectors. It may already be illegal. Furthermore, I believe all apartments must also have CO detectors as well. Known as a silent killer, this gas can go undetected very easily. A CO detector is an important warning system for everybody. I’ve seen smoke/co detectors sold as one detector with a dual purpose function.
Also, consider going over an evacuation route with your tenants in case of a fire and placing an extinguisher in all apartments. Taking time to show people you care about their safety can go a long way.