Hello Terry Andrews:

Referring to Report on U-570 -- HMS Graph, edited by you, the following statement
appears on page 30, Para. 69:

"When charging [electric torpedoes] a [screened] ventilating door [handhole cover] is fitted to the torpedo in place of one of the [regular handhole covers] access doors and the catalyser is used to deal with the hydrogen given off."

What type of catalyser was used?

U.S. battery-powered Mark 18 torpedo [copied from the German G7e] used a built-in ventilation tube using low pressure air, and later, using a hydrogen burner arrangement, when a tube-loaded torpedo had to be ventilated. When the U.S. Mark 28 [passive-acoustic, [copied from German T5] battery-powered torpedo was issued [just prior to the end of WWII], it had palladium catalysts installed throughout the battery compartment to eliminate the continuously accumulating hydrogen.

Awaiting your answer,

ROBERT M.