Filtering respirators are not suitable for spraying isocyanate paints. The respiratory protective equipment (RPE) must be air-fed breathing apparatus.
The device should be a visor-type air-fed breathing apparatus (certified to British Standard EN 14594:2018). It should be Class 4 and should include a low-flow indicator, which may be visual or audible.
Many sprayers lift their visor to check the work they have just completed, not realising they are still surrounded by paint mist. This practice increases worker exposure and must be prohibited if adequate control of exposure is to be achieved.
Visibility through the face piece visor can be assisted by using low-cost tear-off visor covers and by ensuring that lighting in the spray area is sufficient. Lighting can be maintained through:
- covers are kept clean
- lamps are replaced when necessary
If vision is inadequate, then half-mask breathing apparatus (with constant airflow supply) conforming to British Standard EN 14594:2018 may be suitable. A separate visor, to protect against paint splashes, is likely to be required when using half-mask breathing apparatus.
However, it is not clear that a half-mask air-fed breathing apparatus will provide adequate protection in a spray room due to the high levels of isocyanate exposure encountered during spraying. Isocyanate levels can rise into the thousands of micrograms per cubic metre of air.
The use of half-mask breathing apparatus in spray rooms should be allowed only if there is a clear demonstration of risk control through effective and ongoing biological monitoring.
Quantity and quality of supplied breathing air
If an insufficient quantity of air is supplied to the breathing apparatus, it may not provide adequate protection to the user.
The British Standard for visor-type devices does not specify air volume flow rate, but each manufacturer should specify minimum flow conditions in terms of tubing length and internal bore and air pressure. This can be found in the manufacturer's manual.
The low-flow warning device should be designed so that it immediately draws the attention of the wearer to the fact that the apparatus is not supplying the manufacturer's minimum design flow rate.
The COSHH Approved Code of Practice (ACOP) states that air supplied to a breathing apparatus should be tested at least every 3 months to ensure that it meets the standards laid out in British Standard EN 529:2005.
However, there is a higher risk of exposure within the motor vehicle repair sector and a higher risk of contaminants entering the breathing air sector. Specific guidance in COSHH essentials MR02: Spraying 2-pack (2K) products in a spray booth or room advises that breathing line checks are conducted monthly.
It may also be possible to extend the period of inspection if there is sufficient supporting information to provide confidence in air quality. For example:
- previous air quality test results
- location of compressor
- weekly maintenance log to show cleaning of traps
- logging of filter checks and replacements