Enclosing the Air Gap from Formalin Delivery Tubing to Vertical-Flow Fish Egg Incubators Does Not Decrease Aerosolized Formaldehyde Levels

Formalin treatments are frequently used to control water molds during hatchery incubation of salmonid eggs, creating potential occupational safety and health issues. This investigation evaluated the use of a novel technique to enclose the air gap from formalin treatment tubes to 16-tray vertical-flow incubation stacks. Standard formalin treatments of 1667 mg/L for 15-minutes were administered to one, three, or five stacks, both with, and without air gap enclosures. Enclosing the air gap did not significantly reduce aerosolized formaldehyde levels. Even during the treatment of five incubation stacks when formalin amounts were the greatest, mean (SE) peak airborne formaldehyde levels were 1.6 (0.2) mg/L and 1.5 (0.2) mg/L, either with or without air gap enclosure, respectively. The failure of air gap enclosure indicates other techniques are required to decrease aerosolized formaldehyde during formalin treatments of fish eggs in vertical-flow incubators.