Change the filter to a new one if it shows
visible signs of contamination.
Pull the white PTFE filter away from the sensor. Rotating the filter slightly makes it easier to detach.
Use clean instrument air to gently blow any loose dirt and filter material away from the sensor.
Take a new clean filter and push it onto the sensor. If you are using the Vaisala silicone plug for sealing, push and rotate the filter slightly to make sure the filter reaches below the edge of the plug.