Cycling helmets are a safety device designed and tested to prevent injury primarily from impact during a crash. There are clear, accepted testing protocols for testing helmets during an impact crash. Due to the wide variety of conditions that can occur during a crash, including where the crash occurs, the weather conditions, angle of impact, surface of impact, speed, angle of crash, etc., there is currently no approved testing protocol to determine the safety of a helmet, and thus a helmet with modifications, under any conditions other than during an impact.
While there is little research on helmet safety during skid testing, there was a research study conducted by the Director of the Biomechanics Laboratory at Wayne State University that indicated that removable Helmet Covers can increase slide in a crash because removable helmet covers are stripped off the helmet by friction or tear. However, due to the wide variety of factors in any cycling crash, there is not enough information to determine whether a helmet cover will increase or decrease slip and/or injury in a crash.
The veloToze Helmet Cover is made of a thin, lightweight material and is removable. While it is unlikely to interfere with the primary safety function of a helmet, any modification to a helmet, including adding cameras or camera mounts, lights or helmet covers to the outside of the helmet or liners or hats on the inside of the helmet could affect the performance of the helmet. Anyone making modifications to their helmet should do so only after weighing the pros and cons of those modifications.