purchased alarms BUT one of them at night you can see a red glow come out from under every 40-50 sec. green light glows then fades away then red glow

As regards the blinking red lights, here's the answers: RED blinks 4 times per minute (every 15 seconds) - indicates a weak or improperly installed battery. RED blinks 3 times per minute (every 20 seconds) - indicates this unit initiated an alarm in an interconnected system. RED blinks once every 10 seconds - indicates smoke alarm is quieting an unwanted alarm (see FALSE ALARM CONTROL). RED blinks once every second - smoke alarm senses smoke and sounds an alarm simultaneously. RED blinks once per minute (every 60 seconds) - testing for presence of good battery (normal). RED is OFF, but detector in ALARM (sounding) - another smoke alarm in the network has sensed smoke and is signaling an alarm. GREEN is OFF - indicates AC power is not present. Constant GREEN light on - indicates AC power is present. FYI - to change batteries on ANY smoke alarm, you MUST power down the entire system to replace the batteries, then power the system back up after battery is replaced. USE ONE THE FOLLOWING 9V BATTERY MODELS (ONLY): Eveready 216, 522, 1222, Duracell MN 1604 or Ultralife U9VL-J. DO NOT USE RECHARGEABLE BATTERIES!