Storage of partly used closed-circuit rebreather carbon dioxide absorbent canisters

Diving Hyperb Med. 2018 Jun 30;48(2):96-101. doi: 10.28920/dhm48.2.96-101.


Introduction: Diving rebreathers use "scrubber" canisters containing soda lime to remove carbon dioxide (CO2) from the expired gas. Soda lime has a finite ability to absorb CO2. We undertook an experiment to determine whether the manner of storage of a partly used scrubber affected subsequent CO2 absorption.

Methods: An Evolution Plus™ rebreather was mechanically ventilated in a benchtop circuit. Respiratory minute volume was 45 L·min-1 and CO2 was introduced to the expiratory limb at 2 L·min-1. The scrubber canister was packed with 2.64 kg of Sofnolime 797™. Scrubbers were run in this circuit for 90 minutes then removed from the rebreather and stored in packed form under one of three conditions: "open" (unsealed) for 28 days (n = 4); vacuum "sealed" in an airtight plastic bag for 28 days (n = 5); or open overnight (n = 5). Following storage the scrubber canisters were placed back in the rebreather and run as above until the PCO2 in the inspired gas exceeded 1 kPa. The total duration of operation to reach this end-point in each storage condition was compared.

Results: The mean run times to reach an inspired CO2 of 1 kPa were 188, 241, and 239 minutes in the open-28-day, the sealed-28-day and the open-overnight storage conditions, respectively.

Conclusion: Rebreather divers should consider placing partially used soda lime scrubber canisters in vacuum-sealed plastic bags if storing them for longer periods than overnight. If a partially used scrubber canister is to be used again the next day then the storage modality is unlikely to influence scrubber efficacy.

Keywords: Equipment; Hypercapnia; Respiratory; Soda lime; Technical diving.

MeSH terms

  • Calcium Compounds / chemistry*
  • Calcium Hydroxide / chemistry
  • Carbon Dioxide / chemistry*
  • Diving*
  • Humans
  • Oxides / chemistry
  • Respiratory Protective Devices*
  • Sodium Hydroxide / chemistry*
  • Time Factors


  • Calcium Compounds
  • Oxides
  • Carbon Dioxide
  • Sodium Hydroxide
  • Calcium Hydroxide