How do you undertake air disturbance during Asbestos Clearance monitoring?
Introduction
The Clearance inspection process in New Zealand follows the international norm of a four-stage clearance inspection process defined as:
- Stage 1: preliminary check of site condition and job completeness
- Stage 2: thorough visual inspection inside the enclosure/work area
- Stage 3: air monitoring
- Stage 4: final assessment post-enclosure/work area dismantling. (WorkSafe New Zealand, 2016, p. 184)
This blog is looking at the difficulties in achieving the air monitoring component of this clearance process and a potential way forward.
Regulatory framework
Regulation 41 of the Health and Safety at Work (Asbestos) Regulations 2016 (Asbestos Regulations) states:
41 Clearance inspection
(1) This regulation applies if a person commissions licensed asbestos removal work at a workplace.
(2) The person or, if the workplace is a home, the licensed asbestos removalist commissioned by the person must ensure that, when the licensed asbestos removal work is completed, a clearance inspection of the asbestos removal area at the workplace is carried out by,—
(a) in the case of Class A asbestos removal work, an independent licensed asbestos assessor; or
(b) in any other case, an independent competent person.
(3) In this regulation,—
clearance inspection means an inspection (including a visual inspection) of an asbestos removal area after asbestos removal work has been completed to verify that the area is safe for normal use, and—
(a) in the case of Class A asbestos removal work, includes surface testing and air monitoring in a dry condition before the enclosure is dismantled or removed from the asbestos removal area:
(b) in the case of Class B asbestos removal work, may include surface testing and air monitoring
competent person means a person who has acquired, through training and experience, the knowledge and skills of relevant asbestos removal industry practice and who holds—
(a) a certificate in relation to a training course specified by WorkSafe for asbestos assessor work; or
(b) a tertiary qualification in occupational health and safety, occupational hygiene, science, or environmental health. (Ministry of Business, Innovation, and Employment, 2016).
The Approved Code of Practice for the Management and Removal of Asbestos states
“28.4.3 Stage 3
The licensed asbestos assessor or competent person should conduct air monitoring with dust disturbance for Class A asbestos removal work. See section 28.6 for further information…
28.6 Air monitoring
Air monitoring is mandatory for Class A asbestos removal work, and optional for Class B asbestos removal work.
28.6.1 Sample number
The numbers of air samples for conducting air monitoring should be determined on a risk assessment basis. Table 10 recommends sample numbers for air monitoring. It may be necessary to take more samples if the area is subdivided, for example.
|
Enclosure area (m2) |
Enclosure volume (m3) |
Number of samples |
|
50 |
150 |
2 |
|
200 |
600 |
4 |
|
500 |
1,500 |
6 |
|
1,000 |
3,000 |
9 |
|
5,000 |
15,000 |
16 |
|
10,000 |
30,000 |
20 |
Table 10: Recommended sample numbers for clearance monitoring
If the enclosure is less than three metres high, or where exposure is only likely to be at ground level, use the area for calculating the number of samples. In other cases use the volume as the basis for determining the number of samples. If there are large items in the enclosure, subtract their volume from the total before estimating the number of required samples.” (WorkSafe New Zealand, 2016, pp. 184, 186)
The problem
It can be seen above that while there is clear guidance provided as to number of air samples that are required, the Code of Practice only says that air disturbance ‘should’ be undertaken and provides no guidance on how this is to be achieved.
Methods of disturbing air
How can Assessor undertake air disturbance as part of the Clearance (realising that it is not a specific requirement, under either the Asbestos Regulations or the Code of Practice)? Listed below are a number of methods that I have come across with an assessment of their strengths and weaknesses.
|
Method |
Description |
Strengths |
Weaknesses |
|
Leaf Blowers / stationary fans |
The use of a leaf blower is the regulated method, and in the USA. “Prior to air monitoring, floors, ceiling and walls shall be swept with the exhaust of a minimum one (1) horsepower leaf blower.” (United States Environmental Protection Agency, 2003, p. 798) |
Very aggressive disturbance method, potentially releasing all fibres on every surface and in every crevasse.
|
Has the leaf blower been manufactured in a facility that does not contain asbestos, eg not under a failing asbestos roof that is in itself releasing fibres that are entrained in the actual machine (realising that the Membrane filter method does not differentiate from asbestos and other respirable fibres). Unsure how a leaf blower can be decontaminated after being used in an enclosure, especially if the enclosure fails the Clearance Air Test. As there is an electrical motor there is the potential for fibres to be entrained within it. |
|
Hand broom |
The use of brooms to sweep all surfaces is the preferred method in the UK. “Brushing should take place in all of the following locations: all surfaces from where the asbestos has been removed, horizontal surfaces where the dust may have settled or collected or where there is suspicion of surface contamination, and surfaces in close proximity to the sampling equipment.” (Health and Safety Executive, 2005, p. 21) |
Will provide a realistic characterisation of potential fibre release under the worst case normal case usage, i.e. concentrate sweeping of all surfaces. |
Has the broom been manufactured in a facility that does not contain asbestos, eg not under a failing asbestos roof that is in itself releasing fibres that are entrained in the actual machine. Do the broom’s fibres have the potential to release respirable fibres themselves. If a new broom is not used for each test there is the very real potential to transfer contamination from one site to the next. |
|
Clip board |
Most assessors will carry some type of clip board/tablet into the enclosure with them. Some Assessors wave this around to disturb the air. |
All surfaces of the clipboard/tablet can be cleaned prior to entry and exit from the enclosure, thus ensuring no cross contamination between enclosures. |
I have not been able to find any research or guidance on the use of this method, so am not able to comment on its effectiveness, however it is used as disturbance method (Burdett, 2001, p. 27) Anecdotal comments from Assessors indicate that correct use of a clip board may be enough to disturb loose settled dust. However, any compacted and hidden settled dust or in tight spaces may not be able to be captured in disturbance process for a complex site |
|
Plastic bag |
“Most analysts (75%) used a plastic bag to disturb the air, some filled it with air and banged the walls, others flapped the empty plastic bag in the air.” (Burdett, 2001) |
Most removal projects will have plastic bags available to use. The used bag can be left within the enclosure as ‘asbestos waste’, thus ensuring no risk of cross contamination. |
“These practices were shown in laboratory tests, to be very ineffective methods of dust disturbance” (Burdett, 2001, p. iv) |
Discussion
Of the above disturbance methods, the two most effective (through documented investigation and research) are the leaf blower and the broom, however both these methods rely on equipment that may or may not be contaminated or contain other respirable fibres that can jeopardise the fibre counting results. Contamination could arise either from:
- The manufacturing process, eg materials used or facility in which it was manufactured. It is potentially difficult to source brooms and leaf blowers that are certified as ‘free of’ respirable fibres, as it is highly unlikely that this is part of their current manufacturing process.
- Potential for being used previously in another enclosure and not decontaminated or checked for potential sources of respirable fibres (non-asbestos and asbestos) resulting in transporting contamination into the new enclosure.
This potential for cross contamination places the Asbestos Assessor in a difficult position, as if they fail an air clearance whilst using these methods they potentially do not have a solid defence if challenged on the cross-contamination claim, unless they can prove that the tool they used is certifiably clean.
The ‘clipboard’ and ‘plastic bag’ methods can be used with a high degree of confidence that cross contamination will not occur, however the effectiveness of both these methods have their limitations as they depend on the Assessor accessing all spaces. This is especially true in complex sites.
The difficulty in determining a suitable disturbance method, and it not being a specific requirement under either the Asbestos Regulations or the Code of Practice, may be influencing Asbestos Assessors in deciding not to utilise air disturbance in their Clearance assessments.
Potential Solution for further discussion
One possible disturbance tool that has not been mentioned that has potential to be used is a dedicated, modified and fully certified negative air unit or other similar air blowing device. The modification being that the discharge air is directed into a discharge air pipe.
The negative air unit or other similar air blowing device could be placed outside of the enclosure, with the discharge air pipe being fed into the enclosure, via a sealed penetration. Different nossles could be attached to the discharge end dependent on the type of air disturbance required.
At the end of the clearance inspection all that is needed is that the outside of the discharge pipe is wiped clean, as all air inside the pipe has passed through a certified Negative Air Unit and is therefore clean.
This method has the advantage that there is no potential of bring contamination into the enclosure, and different volumes of air can be achieved by using different sizes of negative air units. One difficulty currently is that the Asbestos Regulations do not allow the use of compress air on asbestos, the question would be if this method is defined as using compressed air.
Conclusion
The industry does need a consistent standard in Clearance assessments as each enclosure removal area especially in New Zealand is likely to be very different, and that this must extend to the method of air disturbance. A potential way forward may be that the Code of Practice specifies that air disturbance ‘shall’ be used, and options how it could be undertaken. Furthermore, that the air disturbance is to be undertaken by the Removalist Supervisor under the direction of the Asbestos Assessor.
This way forward has the following benefits:
- The tools used (modified negative air unit, leaf blower, broom, etc) are owned and operated by the Removalist and therefore it is the Removalist’s best interests to ensure that there is no potential for cross contamination with the tools being used.
- Clearance while still being given by the Assessor becomes a team effort between the Removalist and the Assessor. It also requires that the Supervisor must accompany the Assessor for the Clearance inspections.
References
Burdett, G. S. (2001). HSL/2001/11 Improved Methods for Clearance Testing and Visual Assessment of Asbestos Removal Operations. Health and Safety Laboratory, Environmental Measurment Group. Health and Safety Executive.
Health and Safety Executive. (2005). HSG248 Asbestos: The analysts’ guide for sampling, analysis and clearance procedures. Retrieved June 25, 2018, from Health and Safety Executive: http://www.hse.gov.uk/pUbns/priced/hsg248.pdf
Ministry of Business, Innovation, and Employment. (2016). Health and Safety at Work (Asbestos) Regulations (2016). Retrieved March 12, 2018, from New Zealand Legislation: http://www.legislation.govt.nz/regulation/public/2016/0015/19.0/DLM6729706.html
United States Environmental Protection Agency. (2003). Chapter 40, Part 763 -- Asbestos - 2003pt763_0. Retrieved 06 25, 2018, from Code of Federal Regulations: https://www.epa.gov/sites/production/files/documents/2003pt763_0.pdf
WorkSafe New Zealand. (2016, November). The Code of Practice for the Management and Removal of Asbestos. Retrieved March 19, 2018, from WorkSafe: https://worksafe.govt.nz/topic-and-industry/asbestos/management-and-removal-of-asbestos/#lf-doc-29878