Rules about smoke alarms seem to confuse sellers, buyers, and other real estate professionals, so let us go over some basics.
Does the home have functioning smake alarms, and are they in the right place? I do have people ask me that question, but honestly most buyers do not concern themselves with this safety feature. As a home inspector, my job is to check on safety issues, so I am somewhat disappointed when this is not a concern. As a buyer, you have to see what is important to you. Hopefully, you will see that smoke alarms can save your life (they are frequently seen as an annoyance).
I do have one Realtor who I work with, who asks about the smoke alarms on a consistent basis. I never asked him why though. Maybe they helped him one time. Here is the breakdown: you will want one smoke detector in each bedroom and on each floor. They should be wired into the home and together. If a fire breaks out in the third floor bedroom, the alarm would go off in the first floor guest room, so everyone would get out of the home. Even systems wired into the home have batteries in them which need to be changed. Smoke consists of tiny particles which can be detected by different means, but I have never heard of one tpe of detection system working better than another. Smoke detectors are not determing what gas is in the house. If you are concerned about Carbon Monoxide, you need to add a specific detector for that gas. These detectors are usually one per floor.
What happens if I am selling my home, and I only have those individual detectors? Will the home inspector fail me for that? That question bugs me, because we home inspectors do not pass or fail a home. We are reporting on its condition. Here is what I do: I tell my client if the home has smoke detectors meeting the standard to ensure their safety. If there are the appropriate number of smoke detectors in the house, but they are not wired together, I tell the buyer. I have not had a buyer at this point demand that the system which I recommend be placed in the home. I have experienced where one buyer demanded this of a seller (I was working for the seller in this case). The buyer had actually gone overboard in their demands hoping to knock down the price by an incredible amount. I told the sellers that many repairs could be made quickly, and for far less than the buyer’s repair quote, but they could refuse others, like the detectors if they so wished. The buyers would not budge on their demand to greatly lower the price, so the contract fell apart.
Is there a time when the seller has to install a required smoke detector? As it so happens, there is one special case. If the buyer is hearing impaired, the seller is required to have smoke detectors that work with flashing lights, not simply sound. I have never been in this situation, so I cannot say what happens in a typical case. I imagine that the seller may give a discount based on installing such a system rather than have one installed themselves. (This is a rule in Texas. If your state requires this for smoke detectors, you should ask your Realtor or home inspector. To my knowledge, this is not a common rule).
That is the basic overview. Again, I would like to state that it is better to stay safe, and have working detectors in your home, than risk the lives of your family.