Open the main gas tank valve and set the pressure to 4-6 lb with the regulator adjusting screw. This will give a flow rate of 2-3 bubbles per sec into each bag (figs. 1 & 3). Ensure that the pipet tip in each bag is inserted 2/3 into the broth. Tie bubbler tubing for each enrichment loosely together above the baskets to keep the bags standing upright. Bring the water level of the bath up slightly higher than the level of the broths in the bags. Replenish water as needed during the incubation period..