Abstract: Employees #1 and #2, both maintenance workers, were preparing to install a valve and pipe assembly atop a 30 ft high storage tank that contained a mixture of 1/3 animal tallow, 1/3 restaurant grease, and 1/3 acid oil. The employees used a cutting torch to cut into the top of the tank, igniting the gases from the mixture, and causing the tank to explode. The force of the explosion blew one employee approximately 75 ft across the top of the building next to the tank. The other employee was blown into the guardrail, bending the rails and then falling to the tank's concrete pad. Employees #1 and #2 were killed.