Smoke detectors - How to test

I have a 20 year old security system that includes 3 smoke alarms, one is the ion type the other two are optical sensors.
They all blink at regular intervals, seemingly indicating that all is well. Or is it?
I suspect that the blinking lights only indicate that the circuits are working properly. But, does that mean they will actually sound off in the presence of fire/smoke??
How can I be sure that I can rely on them when there is a fire or smoke? Just what does the blinking LED mean??
While googling, I noticed that some people recommend new smoke detectors every ten years or so. Is there any rational need for this, or is it just an urban myth? Many of my electronic components have lasted more than 20 years. Why should smoke detectors conk out after ten years?
--
Walter
www.rationality.net
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Its a myth to replace them by time, my security co wanted me to replace them from a false alarm , when a spider or dust set a false alarm, you gotta know techs make a kickback on selling stuff. Mine can be tested with a magnet, but make smoke and see what happens. A cigarette, a candle, a metal can with something small burning might do it.
Companies make their most money on new instals, and they all are liars, on commission. A good system will last till an electrical part failure or a sensor is crudded up with grease, do your own tests first, my co wanted near 200 $ US a sensor, I said Good By for today, I will check it out. That happened several times in the last 10 years with Honeywell and my 3 false alarms.
So do your own test, its like your New car auto dealer selling you 1000$ worth of uneeded maintenance, which I have seen [ many times] , and they tried to pull on me.
Mine is hard wire, Honeywell, monitored, twice techs were out for dust or spiders setting off false alarms and wanted 1000$ for new sensors for what still works today. Gee I guess I gotta do a 08 check over soon, Thanks for reminding me pal. But dont get suckered, test em your self. Learn your set up. So you dont get suckered.
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