Powers the Petrel. Allow it to boot fully before reading values.

Record baseline raw mV in air before O₂ is introduced.

Below 1.25V the computer may give false readings or shut down mid-dive.

Water in the canister degrades scrubber performance and can cause caustic cocktail.

Pack firmly and evenly — voids allow CO2 channelling and scrubber breakthrough.

Screens prevent scrubber dust entering the loop.

Debris on threads prevents a proper seal and causes loop leaks.

Dry O-rings deform and leak. Use appropriate lubricant only.

Misaligned towers cause gas flow restriction and increased work of breathing.

The counterlung O-rings are a common leak point. Inspect for cracks or deformation before every dive.

Ensure the counterlung is seated correctly and not pinched by the waist strap or wing.

LPI and waist bungees must route between canister and counterlung.

Test by inhaling and exhaling through the closed DSV.

EXHALE → RIGHT tower · INHALE → LEFT tower.

Monitor loop for a period proportionate to dive intensity.

Note if any cell rises slowly — mark it in the worksheet below.