Set out below is a safety notice issued at the end of 1997 by UWI Circle Ltd of Aberdeen, UK. It should be self explanatory, but if you have any queries, please contact the company.
The AH3 and its forerunner AH2 have been in diving use for more than 30 years world-wide. Recent tests on the helmet have indicated that action levels for noise under the existing UK Noise at Work Regulations are exceeded under most diving situations, and that without adequate controls over exposure there is a risk that prolonged use may lead to some hearing deficiency.
Under the UK Noise at Work Regulations the maximum permissible exposure to noise is a function of duration and noise level – e.g. high level for a short period/low level for an extended period. This translates in diving use, to the problem being one of time in the helmet and increasing noise as the greater depth requires higher air flow. Lowering the flow rate reduces the noise level but could give rise to increased CO₂ during the breathing cycle.
An extensive programme to develop a modification to the helmet in order to address the problem has not been successful without incurring other operational penalties. As a result of this the Company has decided to cease supplying the product and advise all current users that the AH3 helmet should not be used unless there are no other more appropriate alternatives identified by risk assessment.
The free flow helmet has largely been superseded in most situations by quieter and more economical demand helmets and the company will provide specific advice to users on equipment appropriate to their needs.
The risk assessments being undertaken by employers of divers using the AH3 helmet should therefore take due regard of this safety notice.
Manufacturers: UWI Circle., 20 Woodlands Drive, Kirkhill Industrial Esate, Dyce, Aberdeen, UK, AB21 0GW.
Tel: + 44 (0) 1224 771 381, Fax: + 44 (0)1224 771 373