1. Pressure Switch: Pressure switches are commonly used in humidifiers to detect the level of humidity and indicate when the humidifier should be turned on or off.

2. Temperature Sensor: Temperature sensors are used to measure the temperature of the surrounding environment and are necessary for proper functioning of a humidifier.

3. Humidity Sensor: Humidity sensors are used to detect the level of humidity in the environment and are necessary for proper functioning of a humidifier.

4. Flow Switch: A flow switch is frequently used in humidifiers to detect the flow of water or air. This information is then used to adjust the settings of the humidifier.

5. Solenoid Valve: Solenoid valves are used to control the flow of water or air into the humidifier.

6. Motor: Motors are used to power the fan that circulates the humidified air.

7. Power Supply: A power supply is required to provide power to the various components of the humidifier.