Annexure 2 

Calculation of Exposure With Regard to the Specified Reference Periods 

This Annexure reproduces the approved method for the calculation of exposure in relation to the 8-hour, short-term and one-year reference periods. 

1.  The 8-Hour Reference Period 

2.  The Short-Term Reference Period 

Exposure should be recorded as the average over the specified short-term reference period and should normally be determined by sampling over that period. Example where the short-term reference period is 15 minutes. 

(a)  Exposure period is less than 15 minutes 

The sampling result should be averaged over 15 minutes. For example, if a 5-minute sample produces a level of 600 ppm and is immediately followed by a period of zero exposure, then the 15-minute average exposure will be 200 ppm: 

(b)  Exposure period is 15 minutes or longer 

Measurements should be taken over a 15-minute period and the result is the 15-minute average exposure. Measurements for periods greater than 15 minutes should not be used to calculate a 15-minute average exposure, but if the average exposure over the longer period exceeds the 15-minute exposure limit, then this limit must have been exceeded over some 15-minute period. 

3.  The One-Year Reference Period for Vinyl Chloride 

Exposure should be recorded as the time-weighted average of vinyl chloride in the atmosphere of a working area over a period of one year. At enclosed vinyl chloride polymerisation plants, continuous or permanent sequential sampling methods must be used. Where discontinuous measurements are made, the frequency of measurements and the number per year should be such that it is possible to state with a statistical confidence coefficient of at least 95% that the true mean annual concentration did not exceed the annual maximum exposure limit. Only periods of plant operation including, where necessary, maintenance time should be taken into account.

Annexure 3

Methods of Measurement and Calculation for Determining the Fibre Concentrations of Man-made Mineral Fibre 

1. The method must determine the exposure of employees by sampling in the breathing zone of the employee exposed. 

2. "Fibre" means a particle with a length > 5 micro m, an average diameter < 3 micro m, and a ratio of length to diameter > 3 to 1, which can be seen using the system specified in paragraph 3. 

3. Fibres shall be counted in accordance with AIA RTM 1. 

4. The results shall be regularly tested by quality assurance procedures to ensure that the results are in satisfactory agreement with the average of results, obtained by approved inspection authorities (AIA) participating in a national quality assurance scheme, using the method specified in paragraphs 1 to 3 above. 

Annexure 4

Cotton Dust

1. The OEL for cotton dust is 0,5 mg m^-3 total dust less fly, 8-hour TWA. This figures is not a personal exposure limit but a background air standard determined by using static samplers. This OEL-RL applies to dust from the processing and handling of raw and waste cotton, including blends containing raw or waste cotton, with the following exceptions: 

(a) Dust from weaving, knitting, braiding and subsequent processes; and 

(b) dust from bleached or dyed cotton. 

1. Under the HCS Regulations, assessors must satisfy themselves that the assessment takes account of people who work intensively with the material e.g. at bale opening, waste handling, maintenance of dust extraction equipment and cleaning procedures, and who are therefore likely to be exposed to dust. 

2. Where the OEL-RL does not apply, exposure should be kept below both 10 mg m^-3 8-hour TWA total inhalable dust and 5 mg m^-3 8-hour TWA respirable dust, determined by a personal sampling method. 

Annexure 5

Asphyxiants

1. Some gases and vapours, when present at high concentration in air, act as simple asphyxiants by reducing the oxygen content by dilution to such an extent that life cannot be supported. Many asphyxiants are odourless, colourless and not readily detectable. Monitoring the oxygen content of the air is often the best means of ensuring safety. The oxygen content of air in the workplace should never be allowed to fall below a minimum of 18% by volume under normal atmospheric pressure. Particular care is necessary when dense asphyxiants, e.g. argon, are used, since very high localised concentrations can arise owing to their collecting in pits, confined spaces and other low lying areas where ventilation is likely to be poor. 

2. Many asphyxiants present a fire or explosion risk. The concentration at which these risks can arise are liable to be well below those levels at which asphyxiation is likely to occur and should be taken into account when assessing the hazards. 

3. Although asphyxiants are listed in Table 2 of Annexure 1, they are not substances hazardous to health for the purpose of the HCS Regulations. 

Annexure 6 

Rubber Fume and Rubber Process Dust 

1. Rubber fume is fume evolved in the mixing, milling and blending of natural rubber or synthetic elastomers, or of natural rubber and synthetic polymers combined with chemicals, and in the processes which convert the resultant blends into finished products or parts thereof, and including any inspection procedures where fume continues to be evolved. 

2. The limit relates to cyclohexane soluble material determined by the method described in "Rubber fume in air, measured as total particulates and cyclohexane soluble material". 

3. Rubber process dust is evolved during the manufacture of intermediates or articles from natural rubber and/or synthetic elastomers. This definition does not include dusts which, for occupational purposes, can be dealt with individually. In each case the relavent OEL will apply. Otherwise, where a substance with an OEL is present in a mixed dust, the OEL for that substance will apply, in addition to the rubber process dust limit. 

4. Methods for personal sampling and measurement of total inhalable dusts are available in "General method for the gravimetric determination of respirable and total inhalable dust and Rubber fume in air measures as total particulates and cyclohexane soluble material". 

Annexure 7 

The Definition of Grain Dust 

1. Grain dust is taken to be dust arising from the harvesting, drying, handling, storage or processing of barley, wheat, oats, maize and rye, including contaminants. 

Acknowledgement to HER BRITANNIC MAJESTY'S STATIONERY OFFICE 

The Department of Labour hereby acknowledges the permission given by the Controller of HER BRITANNIC MAJESTY'S STATIONERY OFFICE (HMSO) for the reproduction of the Crown Copyright material listed below, or part thereof. 

The conditions under which this permission was granted, are subject to the following: 

• The source of the material must be acknowledged; and 

• it must be mentioned that permission for the reproduction of such material was given by the Controller of HMSO. 

List of Material 

1. Guidance note S20 

2. HS(G)61 

3. MDHS 14 

4. MDHS 47 

5. INDG(G)64-L 

6. COSSH assessments 

7. Pesticides: Code of Practice

8. EH14 

9. EH22 

10. EH23 

11. EH25 

12. EH28 

13. EH40 

14. EH42 

15. EH44 

16. EH56