As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB LAVATORY SMOKE DETECTOR WENT OFF. NO SMOKE OR FIRE WAS FOUND BY CREW INSPECTION OF LAVATORY. MAINTENANCE NOTED BLUE HAZE IN CABIN WITH THE APU RUNNING. SUSPECT APU BLEED AIR TO HAVE CAUSED WARNING. PLACED APU ON MEL. ON 8/9/98 BOI MAINTENANCE REMOVED AND REPLACED THE APU. OPERATIONAL TEST NORMAL. CLEAR MEL.