Re: What method of testing can i use to test factors affecting fire alarms?

You've picked a very challenging task.  Smoke detectors usually operate 
with a very low level radiation source that gives off ionized particles.  
A receiver within looks for those particles and reports all is well.  When 
the smoke gets in the sensing chamber, the smoke particles neutralize the 
ions and the sensor notices a change in particles coming into the 
receiving end.  You might check "how things work" web site to get more 
details.

Creating a constant source of smoke would be difficult.  I suppose you 
could put an extinguished candle inside a box and let the smoke go up a 
pipe to a test chamber, but I doubt you could get consistent amount from 
run to run.  You would have to test 5 to 10 times for each detector and 
average the results.  You will find the placement or orientation of the 
detector with respect to the smoke would create more variability.

I would have assumed the detector circuit would be designed to work 
consistently down to the lowest battery voltage allowed by the low battery 
alarm.  They might do this my using a circuit that cuts the 9v battery 
voltage down to 5v to run the circuit.  If you could get a consistent 
smoke, you could test this by hooking up a variable DC voltage to the 
input or use a resistor voltage divider circuit to create a lower voltage 
from the battery.


----resistor--------
|            |      |
detect       |      battery
|           res     |
|            |      | 
____________________


By changing the values of the two resistors, you can change the voltage to 
the detector.

You might try researching Consumer Reports and see if they ever tested 
smoke alarms and how they did it.

I suspect location of the smoke detectors and dead batteries are the 
reason they might not go off in a house fire.

Mr. Stana