In a cordless power tool system, high temperature gases created in a battery pack by the battery cells during a charging or discharging operation can be routed into a housing of one of an attached power tool or charger to reduce the temperature of the gases, prior to venting the gases externally. In an example, a battery pack has at least one vent hole for relieving pressure and a movable device covering the vent hole and configured to expose the vent hole upon a pressure set-point within the pack housing being exceeded. In another example, the pack housing includes a thin-walled section designed to break if pressure within the pack housing exceeds a given pressure setpoint. In a further example, the pack housing includes a baffle having an S-shaped cross-section for providing a vent path for gases and for preventing external fluids from entering the pack housing.