What happens to the diaphragm during the inhalation cycle of the MMR?

During the inhalation cycle of the MMR (positive pressure mask-mounted regulator), the diaphragm plays a crucial role. As the user inhales, the diaphragm moves down. This action creates a negative pressure that activates the demand lever, pressing down on it. The demand lever then opens the flow path for air to enter the mask, allowing the user to breathe in air from the SCBA.

The mechanism is designed to ensure that as long as the user inhales, the flow of breathable air is initiated, which is vital in maintaining a constant supply of oxygen in environments where air quality may be compromised. The diaphragm's movement in that direction is essential for the effective operation of the SCBA system.