Trying to smoke test an old First Alert SA76RS

Hi guys as most of you know last October I acquired an old First Alert SA76RS smoke detector serial number 415115 meaning it has to be an earlier model going back to 1977. I am able to successfully set it off by pushing the button and I have done with both cover on and off and I love the high pitched squeal now which was one of my childhood fears. I want to set it off with a smoke test and I have tried several times using candle smoke but it won’t sound. Can someone please tell me what I am doing wrong? I know a push button test just usually tests the circuit board. Maybe the detector is too old to smoke test? Any advice please let me know because I want to try and smoke test it soon in a video. Either way it is a cool smoke detector and thanks to bmccorkle who is not a collector and I am I finally have this detector. Take care for now.

Jan