What's the Burning Smell Coming from my Electric Ryobi Belt Sander?

Safety First: Disconnect from power  

Important: Always wear the correct protective equipment before maintenance. Dust mask or respirator P2, FFP2, or N95. 

Motor Smell During Use 

From new, electric motors often produce a smell which is normal and will disappear after several uses of the tool. 
This smell can also occur after extended periods of heavy use. 

Allow the Motor to Cool 

Sanders are typically used for long periods and need regular breaks to prevent overheating. 
If the motor overheats repeatedly, it could eventually burn out. 
Example: After 30 minutes of continuous use, allow a 5–10-minute rest before resuming.