Storage batteries subject to the provisions of this standard must be securely attached to the conversion vendor unit or medical unit. They must be installed in an area which is vapor-tight to the interior and ventilated directly to the exterior of the unit. When batteries are installed in a compartment, the compartment must be ventilated with openings of not less than two square inches at the top and two square inches at the bottom. Batteries must not be installed in a compartment containing spark or flame producing equipment, except in an engine generator compartment if the only charging source is the generator itself.