Detach the Polar Transmitter Module from the chest strap after use. Then rinse the chest strap under running water and hang to dry. Clean the Polar Transmitter and chest strap with a mild soap and water solution when needed. Never use alcohol or any abrasive material (steel, wool or cleaning chemicals) on the module or the strap. Store both items separately to maximize battery life. Further instructions can be found at the link below.

https://support.polar.com/us-en/support/maintenance_of_heart_rate_sensor_with_textile_strap