Exposure limits for air diving operations

Contents

• Introduction
• Exposure limits for air diving operations
• Further reading

Introduction

1 This diving information sheet is part of a series of information sheets providing guidance on diving at work. It replaces the following diving safety memorandum: DSM 2/1990. The remaining DSMs have either been replaced by other diving information sheets, or will be cancelled when the Diving at Work Regulations come into force on 1 April 1998.

2 The sheet contains guidance on the maximum time that a diver, using air, should spend under water.

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Exposure limits for air diving operations

3 HSE's policy is to recommend that diving, which uses air, should be organised in such a way that the planned bottom times* do not exceed the limits outlined in Table 1.

4 If a nitrox breathing mixture is being used, you can find out the maximum exposure by entering the equivalent air depth of the maximum dive depth in the table below.

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Table 1 Maximum bottom time limitation for surface decompression, in-water decompression, and transfer under-pressure decompression diving
Depth		Bottom time limits (minutes)
Metres	Feet	Transfer under-pressure	Surface decompression and in-water decompression
0-12	0-40	240	240
15	50	240	180
18	60	180	120
21	70	180	90
24	80	180	70
27	90	130	60
30	100	110	50
33	110	95	40
36	120	85	35
39	130	75	30
42	140	65	30
45	150	60	25
48	160	55	25
51	170	50	20

* Bottom time:the total elapsed time from when the diver is first exposed to a pressure greater than atmospheric, ie when leaving the surface, or on the start of pressurisation when a closed bell is employed in the observation mode, to the time (next whole minute) that the diver begins decompression (measured in minutes).

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Further reading

1. Commercial diving projects offshore. The Diving at Work Regulations 1997. Approved Code of Practice L103 HSE Books 1998 ISBN 0 7176 1494 8
2. Commercial diving projects inland/inshore. The Diving at Work Regulations 1997. Approved Code of Practice L104 HSE Books 1998 ISBN 0 7176 1495 6
3. Recreational diving projects. The Diving at Work Regulations 1997. Approved Code of Practice L105 HSE Books 1998 ISBN 0 7176 1496 4
4. Media diving projects. The Diving at Work Regulations 1997. Approved Code of Practice L106 HSE Books 1998 ISBN 0 7176 1497 2
5. Scientific and archaeological diving projects. The Diving at Work Regulations 1997. Approved Code of Practice L107 HSE Books 1998 ISBN 0 7176 1498 0
6. The Diving at Work Regulations 1997 SI 1997/2776 The Stationery Office 1997 ISBN 0 11 065170 7

HSE priced and free publications are available by mail order from:

HSE Books, PO Box 1999, Sudbury, Suffolk CO10 6FS

Tel: 01787 881165 Fax: 01787 313995

HSE priced publications are also available from good booksellers.

For other enquiries ring HSE's InfoLine Tel: 0845 345 0055 , or write to HSE's Information Centre, Broad Lane, Sheffield S3 7HQ

HSE home page on the World Wide Web: http://www.open.gov.uk/hse/hsehome.htm

This leaflet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

This publication may be freely reproduced, except for advertising, endorsement or commercial purposes. The information is current at 2/98. Please acknowledge the source as HSE.

Printed and published by the Health and Safety Executive 2/98 DVIS5 C20

Added to the Web Site on 23/9/1998

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