DOT helmet refers to motorcycle helmets that meet the standards of the United States Department of Transportation (DOT). DOT helmets must pass DOT certification tests to ensure they meet certain safety performance requirements. These tests include requirements for impact absorption, field of vision, helmet retention, strap retention, and other aspects. Only helmets that pass these tests and obtain certification can be legally sold and used in the United States. DOT helmets typically bear a DOT certification mark on the helmet, which consumers can check to confirm if the helmet meets DOT standards.

The standard requirements for DOT helmets include:

1.The helmet must provide sufficient protection to effectively reduce the risk of head injury.

2.The helmet must have sufficient impact resistance to withstand certain forces in accidents.

3.The helmet must have sufficient stability to remain stable during high-speed riding and not easily come off.

4.The helmet must have sufficient ventilation and comfort to remain comfortable during riding.

5.The helmet must meet certain size and weight requirements to accommodate the needs of different riders. 

When purchasing a DOT helmet, consumers can check for the DOT certification mark on the helmet to ensure it meets DOT standards. Additionally, DOT helmets also need to undergo regular inspection and maintenance to ensure the effectiveness of their protective function.