There are some cheats with this too. A lot of time duct detectors get installed in locations that are hard to access. With the duct detectors currently out there, less than 50% get tested correctly because of access issues. They're hard to get to but there's a solution for that. If you have some interest in fixing your problems with getting to the duct detectors, there are products that can be used remotely from the duct and still sense smoke in the duct. Another cheat is using a remote test switch. It's not a code required thing. You don't have to have it there but it's an option. Any duct detector that's concealed needs to have a remote indicator lamp. A test switch has this remote indicator lamp that would light up red if the detector is activated. That would help during investigation of a false alarm, but the remote test switch is to test the interface between the duct detector and the shutoff relay to the air handling unit. We can test it that way, but it doesn't replace the smoke entry test, or the sensitivity test to make sure that the duct detector actually works. It just tests the interface between the two, although a lot of people use that as their actual test but I would say it doesn't meet the intent of the code.