Air Carrier flight crew reported while following the dry ice procedures for packs operated by APU before and during engine start; the carbon dioxide monitors indicated increased levels. The flight crew recommended procedures be revised to clarify the 'Pack ON/OFF' position during engine start and departure.
Synopsis
Air Carrier flight crew reported while following the dry ice procedures for packs operated by APU before and during engine start; the carbon dioxide monitors indicated increased levels. The flight crew recommended procedures be revised to clarify the 'Pack ON/OFF' position during engine start and departure.
Narrative
Prior to block out; received Dry Ice waiver to use Dry Ice Supplemental Procedures. FO (First Officer) and I reviewed the flight manual; Dry Ice Dispatch Increased Carriage Limitations; the Dry Ice Supplemental Procedures; and the Drager PAC 7000 CO2 Monitor Alerts as listed in the Supplemental Procedures in the QRH. All was normal until just prior to block out with the APU running and the doors shut; we had 2 minor maintenance issues that delayed our block out. While addressing the maintenance issues; the Drager monitors began to signal increased CO2 levels. We elected to reopen the doors since maintenance had to come aboard to address the maintenance issues; and since the FO commented that he was beginning to feel mild effects of the increased CO2 levels. One Drager monitor (FO) increased to .8; the other Drager monitor (Capt) remained at 0; and did not go off. We had positioned the third monitor in the jumpseat area and it also began to alert. Opening the doors with the APU air and packs still on alleviated the increased CO2 levels; the Drager monitors all indicated 0; the FO commented that he again felt fine with no effects of the prior increased CO2 levels; the maintenance issues were resolved; and we discussed next steps. The Dry Ice Supplemental Procedures in the QRH discuss the option to use Air System Manual - Air Conditioning Manual operation after each engine start to minimize the time with no or low airflow on the airplane; discusses the option for a Packs ON takeoff to maximize ventilation; etc.; but indicates in the verbiage that 'Packs OFF should not present a problem.' We were aware of the options; discussed mitigation strategies; and came up with a plan should the Drager monitors indicate increased CO2 levels after blockout. We assumed that the time to start the engines; and the time from takeoff to the packs coming pack on after takeoff would be so minimal; that we would not need to do a Packs ON takeoff or use Air conditioning Manual procedures during engine start; especially with the QRH statement that 'Packs OFF should not present a problem.' We pushed back; started normally; some of the Drager monitors again began to indicate increased CO2 levels of about .5; one still indicated 0. When the engines were started and the packs came back on; the Drager monitors again quickly went to 0. We felt no ill effects; discussed our plan; again consulted the QRH supplemental procedures; and elected to continue. After takeoff during climb out; the Drager monitors again began indicating low levels of CO2 at approximately .5; but they quickly went back to 0 and stopped indicating increased CO2 concentrations soon after the packs came back on.Over reliance on QRH Supplemental Procedures that should probably be slightly more conservatively written so as to not give the impression that 'Packs OFF should not present a problem.' and should RECOMMEND the use of Air Conditioning - Manual during engine start and a PACKS - ON takeoff.Suggestions: Small changes to the QRH Dry Ice Supplemental Procedures eliminating the 'Packs OFF should not present a problem.' statement and not only presenting the option; but RECOMMENDING Air Conditioning Manual Operation during engine start AND a PACKS - ON takeoff. Both would mitigate the presence of increased CO2 levels; decrease distractions; and streamline our procedures and define a specific path when presented with the increased Dry Ice levels leading to the use of Dry Ice Supplemental Procedures. In hind sight; if I were presented with this situation again; I would have preferred to use both Air Conditioning Manual Operation during engine start AND a PACKS - ON takeoff; and if the QRH procedure had RECOMMENDED both and not suggested that 'Packs OFF should not present a problem'; I would have chosen that path. This change would minimize delays; eliminate distractions; and make our Dry Ice Supplemental Procedures safer.
Second reporter narrative
I was the First Officer on Aircraft X. During preflight; we were advised that our flight would be operated under supplemental Dry Ice procedures. The Captain and I reviewed the FOM; Dry Ice Dispatch Increased Carriage Limitations; the Dry Ice Supplemental Procedures; and the Drager CO2 Monitor Alerts as listed in the Supplemental Procedures in the QRH. During our initial block out attempt; we closed all the doors; conducted a few remaining briefing items and completed the before start checklist; all with AC Packs on from APU air. Once we selected ignition on; the air controller shut off the air to the packs; but it was at this point that we started working another maintenance issue. I was surprised about the onset of the CO2 monitors indicating elevated levels in the cockpit. Shortly after when the air was shut off; my monitor starting beeping (at first I thought I had just breathed on it) and soon after the monitor we had placed in the jumpseat area started beeping (no jumpseaters however). The levels on my monitor climbed to around .8 pretty quickly. While we were trying to get the air back on and working the other maintenance issue it was at that point that I started to feel minor effects of the increased CO2 levels in the cockpit; and the third C02 monitor (Captains) started going off. I estimate that this all took place within about 3 minutes of the air turning off. Furthermore; it took a couple minutes of airflow to lower the CO2 levels. Once air was reintroduced to the cockpit I started feeling better quickly. Of note; during this sequence the aircraft had not moved. The Captain and I disarmed the doors to work the maintenance issue and ran the APU air to continue providing air flow. The Captain and I discussed my health and continuing; which at this point I was not feeling any ill effects so we elected to continue. Upon second block out; we expedited the time with the air off for engine start and even still got some C02 increased level alerts on two devices. Again; whenever airflow was cutoff; shortly after the C02 monitors started indicating elevated levels. We did not move the aircraft at any point while the CO2 monitors were at all indicating elevated levels. After takeoff; we got again got an indication of elevated levels in the jumpseat compartment until the packs turned back on. Finally; when we parked at spot X in ZZZ1; we had to wait about 20 minutes for a stair crew to arrive. Per the Captain and I's plan; we started the APU on landing and had no disruption in airflow once we parked and shut down. However; after about 15 minutes following shutdown while we were waiting for a stair crew; WITH all packs operating from APU air; we started getting increased CO2 level indications from two monitors. Thankfully at this point the stair crew had arrived and was starting to position the stairs so we elected to wait it out. Cause: increased CO2 levels in the aircraft from carrying over 3000 lbs of dry ice. This was exacerbated by a period of about 20 minutes that the aircraft doors were closed and all packs were operated under APU air before block-out.Suggestions: I've operated under Supplemental Dry Ice procedures before but this is the first time that the monitors have indicated elevated CO2 levels and that I've felt the effects. Before all this happened; the Captain and I came up with a plan; based on the QRH; that we thought was adequate. Unfortunately; I think in our situation; the QRH was inadequate in helping us prepare our plan to mitigate the increased dry ice amounts which increased confusion about what was happening and resulted in myself feeling the effects. Of note; we had quite a bit of dry ice loaded close to the front of the plane. From my memory; we had 3L position loaded with +1300 lbs of dry ice. I'm not sure if this presents a greater risk to the crew being loaded close to the front. A couple of recommendations that would have helped the Captain and I come up with a Dry-Ice mitigation plan that would have been more realistic in our situation.Recommend adding a maximum time period with aircraft fully closed and operating on APU air. Judging by our block in experience at ZZZ1; around 3000 lbs of dry-ice started elevating CO2 levels; with APU air/3 packs operating within 20 minutes. At a certain point; and in our situation; letting the cargo compartment air out (with APU running) for a few minutes; while maintenance had to work on our plane; would have been a prudent procedure to implement. This might have reduced levels in the aircraft enough so that we weren't constantly dealing with our CO2 monitors going off.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.