contamination
Silver, sorry but my comment about ground contamination wasn't related to your point.
I was refering to NTSB discussion involving spurious smoke detection which is all about the Avionics bay fire detection (see above NTSB report linked) and the following Airbus procedure ; it's not about the toilets that one can avoid being flagged while smoking.
Indeed, most of false AVNCS SMOKE triggered in flight were due to contamination on the ground released after the take-off phase. And it's an old discussion lasting since a while.
My other point was to underline that both Lavatories and Avionics were detected in MS 804 ACARS, almost simultaneously, and several hours after take-off. It's unlikely related with someone trying to smoke in lavatories that get the smoke detector warning in Avionics bay triggered.
TFU 26.15.15.001 in July 1999
*DESCRIPTION: SOME OPERATORS HAVE REPORTED MANY CASES OF SPURIOUS AVIONICS SMOKE WARNINGS, LEADING TO "AVIONICS SMOKE" OR "LAND ASAP" ECAM MESSAGES. THESE WARNINGS HAVE MAINLY BEEN REPORTED ON GROUND, HOWEVER THERE HAVE BEEN A FEW CASES GENERATED IN FLIGHT, SHORTLY AFTER TAKE-OFF AND GEAR RETRACTION.
*CONSEQUENCES: N/A
*INVESTIGATION STATUS: THE AIRCRAFT FLIGHT PHASE CONFIGURATION WHERE AVIONICS SMOKE WARNINGS HAVE BEEN GENERATED FALL INTO TWO MAIN CATEGORIES; ON GROUND AND TAKE-OFF.
- ON GROUND - WITH THE AIRCRAFT ON GROUND THE AVIONICS VENTILATION IS SET TO 'OPEN LOOP', WHEREBY OUTSIDE AIR IS USED TO PROVIDE VENTILATION FOR THE AVIONICS COMPARTMENT. IN ENVIRONMENTS WHERE HIGH HUMIDITY AND/OR CONTAMINATION EXISTS (JET EFFLUX/BLOWN DUST ETC). IT IS POSSIBLE FOR THE SENSITIVITY OF THE AVIONICS SMOKE DETECTOR TO BE AFFECTED CREATING AN ALARM CONDITION.
- TAKE-OFF - THE AVIONICS SMOKE WARNINGS ARE INHIBITED FROM 80KTS TO 1500 FEET. DURING THIS TIME IF THE AVIONICS DETECTOR GOES INTO ALARM THEN A 'LAND ASAP' (IN AMBER) IS GENERATED ON ECAM. THE ONLY WAY TO IDENTIFY THE CAUSE OF THE AMBER WARNING IS BY DEPRESSING THE RECALL BUTTON ON THE ECAM CONTROL PANEL. INVESTIGATIONS HAVE DETERMINED THAT SOME OF THESE 'LAND ASAP' WARNINGS HAVE BEEN GENERATED DUE TO A PREVIOUSLY LATCHED, BUT INHIBITED AVIONICS SMOKE WARNING THAT HAD BEEN GENERATED WHILST THE AIRCRAFT WAS ON GROUND. INVESTIGATIONS HAVE SHOWN THAT THE IONIZATION TYPE SMOKE DETECTORS SENSITIVITY IS SUBJECT TO THE AMBIENT TEMPERATURE, PRESSURE AND AIR CONTAMINATION WITH MOISTURE, DUST OR POLLUTION. THE HIGHEST SENSITIVITY TRANSLATED INTO A VOLTAGE SHIFT BEING ON THE GROUND AND DURING TAKE-OFF.
*INTERIM SOLUTION: N/A
*MAINTENANCE ADVICE: IN CASE OF AN 'AVIONICS SMOKE' WARNING TRIGGERED AND LATCHED ON GROUND, FWC1 AND FWC 2 SHOULD BE RESETED ONE AT A TIME BY MEANS OF THEIR C/B (3WW C/B 49VU FOR FWC1 AND 2WW C/B 121VU FOR FWC2). THIS WILL CLEAR THE LATCHED CONDITION OF THE WARNING IF THE AVIONICS SMOKE CONDITIONS HAVE DISAPPEARED. THEN AN UNDUE 'LAND ASAP' ALARM WILL BE AVOIDED. OPS ADVICE: N/A REPERCUSSION ON A/C DISPATCH: N/A PERMANENT OR FINAL SOLUTION: A NEW GENERATION OF SMOKE DETECTOR PN CGDU2000-00 USING AN OPTICAL TECHNOLOGY HAS BEEN DEVELOPED IN ORDER TO REPLACE THE 'OLD' GENERATION OF IONIZATION TYPE SMOKE DETECTOR. THIS NEW GENERATION TYPE OF SMOKE DETECTOR HAS A DIFFERENT TRIGGERING PRINCIPLE AND IS THEREFORE NOT AFFECTED BY THE TEMPERATURE AND PRESSURE CONDITIONS. IN SERVICE EVALUATION (6 MONTH PERIOD) OF AVIONICS OPTICAL SMOKE DETECTOR PN CGDU2000-00 HAS BEEN PROPOSED TO TWO OPERATORS. DEDICATED SB A320-26-1052 HAS BEEN RELEASED MID JULY 2000. THE IN SERVICE EVALUATION HAS BEEN COMPLETED SUCCESSFULLY. SB A320-26-1052 REVISION HAS BEEN RELEASED THE 30TH OF AUGUST TO INCORPORATE ALL AIRLINES IN THE EFFECTIVITY.