Remote terminals are vented to prevent that. There are fans constantly pulling air up and out of the cabinet.
FWIW Most newer cabinets (MESA etc.) are sealed the inside air is recirculated and is not exchanged with the outside atmosphere. In order to keep the electroincs cooled they use heat exchangers not fans connected to the outdoors. This helps to keep the interior dry and nice and clean.
Last year I heard of a MESA 4 that exploded when a tech opened the door. Investigation revealed the charger/alarm failed and battery string had gone into thermal runaway filling the interior of the cabinet with hydrogen gas when the tech opened the door something sparked and the rest was history.
As for gas that can also be a problem most cabinets have conduit running from them and if not properly sealed sewer (methane) gas can migrate up the pipe from the manhole and into the cabinet add one spark from a relay contact and boom it’s all over for that RT.
Wayne -- If you cannot fix it with a buttset and some beanies you ain't a technician.
