Date: 201403
Local time of day: 1801-2400
Location: SAN.Airport, CA
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Mission: Cargo / Freight / Delivery
Flight phase: Taxi
ATC / advisory: Ground SAN
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Training / Qualification
Second reporter function: Captain; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Company Policy; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: Operating [a one plus hour flight] in a B-757 under a dry ice waiver. Allowed up to 1408 Kgs on main cargo deck provided no live animals and CO2 monitors are used. During pushback and engine start (packs off); both the Captains and First Officers CO2 monitors alerted. Highest levels noted were .6% for the Captain and .7% for the F/O. We continued with the engine start; immediately brought the packs online and opened the cockpit windows. The alerts ceased within 30 seconds. We spoke to Dispatch and the duty officer and concluded it was safe to continue based on two operating packs and the availability of supplemental oxygen. The scheduled flight was conducted without further incident. Unsure; at this time; how the warnings occurred so quickly after closing the airplane for departure. The activation of both monitors seems to preclude a spurious alert. One would think the rigid cargo barrier would afford more protection. Not sure what actually caused the event. We obviously had quite a bit of dry ice aboard. I mistakenly thought the rigid cargo barrier and normal ventilation would take care of most of [the CO2]. The speed at which the monitors alerted was surprising. Fortunately we were almost complete with the engine start and the packs were quickly available. Also; the Captain opened his window which I'm sure helped. Maybe we should look at our dry ice limits and aircraft air circulation specifics; especially during engine start when the packs are not operating. Opening a window; while helpful; is not always feasible. I have no intention of flying complete legs on supplemental oxygen.  Further; we should have some real; hands on training with the new monitors and what each alert means. A bulletin is not cutting it when personal safety is concerned.


Second narrative: We had a dry ice waiver for this flight. On push back during 2nd engine start with the packs turned off; the CO2 monitor of both the F/O and the Captain alerted. The F/O monitor reading was 0.7 and the Captain was 0.6. I opened my window and directed the F/O to turn the packs back on. After turning the packs back on the concentration level started to decrease. The levels continued to decrease after closing the cockpit window to 0. We referenced the bulletin concerning the CO2 monitors and called Dispatch to discuss the incident. After speaking with Dispatch and the duty officer we decided it was safe to continue with both packs operating and oxygen available.


Synopsis: B757 flight crew reports flying a one plus hour flight with a dry ice waiver and the crew wearing CO2 monitors. During engine start both monitors alert and the Captain opens his window and the packs are turned on when available. The CO2 concentration quickly drops to zero from .7% and the flight departs.