B767-300 captain reported returning to the gate after the crew's CO2 detector alarmed because of a l...

Narrative:

During preflight we were notified of total dry ice of 1229 KG and a waiver was issued. Max without waiver is 966 kg. First officer preflight and wore the CO2 detector. On pushback with packs off and starting engines his detector alarmed level 1 with .8 registering. Just to make sure it was not malfunctioning we turned the extra monitor on and it too alarmed. Told pushback crew to bring us back in gate and we shut down engines. Turned AC packs on and opened fos window for ventilation as towed back in gate. Conferred with the hazmat specialist; maintenance; ground operations; and dispatch. Concluded to take off pallet position 3L which had majority of dry ice containing 861.7 kg. Continued on flight after receiving proper paperwork and redoing our preflight duties. No further issues.excessive dry ice near cockpit causing monitor alarms to go off. I've carried a lot of dry ice using waivers and never had this problem. Not sure why this time it set alarms off. Prevention methods would be to carry less and maybe move it further back from flight crew; or in belly.

Original NASA ASRS Text

Title: B767-300 Captain reported returning to the gate after the crew's CO2 detector alarmed because of a large quantity of dry ice that had been loaded under waiver.

Narrative: During preflight we were notified of total dry ice of 1229 KG and a waiver was issued. Max without waiver is 966 kg. FO preflight and wore the CO2 detector. On pushback with packs off and starting engines his detector alarmed level 1 with .8 registering. Just to make sure it was not malfunctioning we turned the extra monitor on and it too alarmed. Told pushback crew to bring us back in gate and we shut down engines. Turned AC packs on and opened FOs window for ventilation as towed back in gate. Conferred with the HazMat specialist; maintenance; Ground operations; and Dispatch. Concluded to take off pallet position 3L which had majority of dry ice containing 861.7 kg. Continued on flight after receiving proper paperwork and redoing our preflight duties. No further issues.Excessive dry ice near cockpit causing monitor alarms to go off. I've carried a lot of dry ice using waivers and never had this problem. Not sure why this time it set alarms off. Prevention methods would be to carry less and maybe move it further back from flight crew; or in belly.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1468880
Time
Date	201707
Local Time Of Day	1801-2400
Place
Locale Reference	BOS.Airport
State Reference	MA
Aircraft 1
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Procedural Published Material / Policy Deviation - Procedural Hazardous Material Violation Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

B767-300 captain reported returning to the gate after the crew's CO2 detector alarmed because of a large quantity of dry ice that had been loaded under waiver.