HVAC controls and thermostats regulate the HVAC system and help ensure occupant comfort through efficient operation. Thermostats monitor the temperature of a space or sensor and control the HVAC system to maintain a desired temperature. HVAC sensors and switches react to environmental changes and send control signals to the HVAC system. HVAC hydronic valves regulate the flow of fluids and gases through hydronic HVAC systems. Steam system traps and vents remove air and water from steam-based heating systems to improve their efficiency. HVAC equipment controls and components regulate specific components of the HVAC system to ensure safe operation. Actuators for dampers and valves change the position of connected HVAC components and allow them to be controlled remotely. Pneumatic controls use compressed air to send control signals in hazardous environments.