Posted By TBC I've always been told and believed that there is something in the adhesive of ‘certain’ stickers that can help breakdown the molecular structure of the helmets (You can get some that don't). I was with BP Chemicals at the time and have no reason to doubt the source of information. We also insisted that no felt tip pens were used to write or draw on them for the same reasons and that they could only be washed, if needed in soapy solution (no solvents). It goes without saying that some will also try and spray paint their helmet to be different. Again this will cause damage. The message also went out that anyone causing this kind of abuse or damage would be subject to disciplinary action for interfering or damaging items provided (PPE) for employee protection. Being in an environment with petro-chemicals we also used to insist on the helmet being replaced approx every three years even if no damage was visible. Hope this helps. It certainly prevents employees using the helmet to write and advertise all forms of graffiti.