What are PDIs on the Smoke Detector?

• A. Green power indicator light illuminated
• B. Nothing is blocking the smoke detector
• C. Both the green power indicator light illuminated and nothing is blocking the smoke detector
• D. The red alarm indicator is blinking

Answer: (C)

PDIs check two things at once: that the detector has power and that nothing is blocking the sensing path. The green power indicator being illuminated shows the unit is powered and able to operate. At the same time, having nothing blocking the detector ensures air can reach the sensing chamber so smoke can be detected promptly. When both conditions are true, the detector is in a proper operating state. A blinking red alarm light signals an actual alarm condition, not a normal PDI status, so it doesn’t describe the standard PDI check. That’s why having both the green light on and no obstruction is the best answer.