The Health and Safety Executive (HSE) guidance on blasting techniques was released a few years ago by the Asbestos Liaison Group (now the Asbestos Leadership Council) as appendices to meeting minutes. This approach was a handy way of releasing the guidance without all of the pesky red tape that normally plagues official documents. Alas, even this route has now closed – evidenced by the fact that the last one was well over a year ago.
I wrote about the guidance at the time. Technology has changed over the last few years, but the original document started with the recognition that blasting may be required in a few rare circumstances. It also emphasised that the process should only be considered as a last resort, and that it shouldn’t be regarded as a go-to solution.
The guidance also insisted that the use of processes like Quill, Torbo or ice (above other more traditional approaches) must be fully justified by the licensed contractor, with evidence in support. What this translates to is that the method must not merely address and mitigate the significant additional hazards, but that the reasons for introducing them in the first place must be declared and justified.
It’s important to consider those additional hazards, which typically include:
- High fibre release (HSE results suggest typically 4-10f/ml, but it can be up to 20f/ml)
- Difficulty conducting mandatory personal monitoring because of the dust and water vapour released during the procedure
- Noise (>85dB(A))
- Heavily reduced visibility from dust and water vapour condensation. This reduces the supervisor’s ability to supervise the works
- Increased manual handling (holding the lance, but also moving the ‘garnet’ around)
- Risk of enclosure breach
- Increased risk of blocked negative pressure unit (NPU) filters due to dust and moisture (leading to inadequate ventilation)
- With dry ice, high levels of carbon dioxide – an asphyxiant and source of positive pressure
At the time there was also a concern about potential high vibration at the lance end. This concern however seems to have been unfounded, or at least it has been mitigated by newer devices. A recent HSE case study has found no significant vibration exposure from the technique.
Regardless, other concerns remain: in particular the potential for very high exposure, and the inability to effectively conduct personal monitoring or supervise the works. So why would anyone still consider blasting?
Clients and analytical consultants are normally the main driver when it comes to blasting, often due to an eagerness for ‘an asbestos-free building’. It would therefore be wise to involve them more fully in the decision making process, and explore whether their reasons for wanting to be asbestos-free outweigh the added hazards from blasting.
Ultimately, the guidance says that blasting should be justified, and that robust processes should be in place to ‘prevent misuse’. Or to put it another way, there should be a review of the justification, and it should be signed off by senior management. The technique must also be declared on the ASB5.
On a more practical level, the amount of waste the technique generates is quite astounding. The contaminated grit is heavy and requires frequent clean up. In addition, the grit itself can impact into the surface you have cleaned – requiring extensive fine cleaning. If you are not very careful, the grit can be blasted beyond the boundaries of the enclosure – spreading the problem by contaminating hard-to-access voids.
New technology making a difference
Blasting clearly presents contractors with additional challenges that make it anything but a silver bullet, and the tightening guidance has generally made it less suitable, more of the time. However, since I last wrote on the subject, new equipment that has become available that could offer a potential lifeline.
For example, Beacon’s smart recirculating NPU is an astonishing piece of kit that allows for prodigious number of air changes – vastly more than the traditional approach. Graham Warren of ACAD wrote a very good summary of how the system works, and how it can improve working conditions in the enclosure.
From the perspective of blasting in particular, the really clever bit is that the Beacon’s NPU combines recirculation and an inline heater. This means that the air inside the enclosure can be kept above the dew point – preventing condensation and drastically reducing the visibility issues and the barrier to personal monitoring.
But while the vibration issues of blasting are less of a concern, and visibility and air testing are much improved, there still remain many issues. If you’re still considering the technique for a project, you should refer to the list of additional controls suggested in the original guidance – I discussed these in my earlier article.
Gunning for blasting
Still, as any H&S professional will tell you, the first thing you should consider is elimination. And in this case, technology improvements among needle guns may make it easier to eliminate blasting as an option.
While blasting requires a huge trailer, needle guns – such as the Trelawny VL303 Needle Scaler, with an electric compressor and dust cowl – are much more portable and convenient. Trelawney’s solution is low vibration, allowing for more than eight hours’ trigger time, and the H-type vacuum attachment ensures that the dust and waste generation is minimal.
So could improved needle guns finally end the need for blasting? Both techniques are slow going, but I’ve spent time talking to supervisors proficient in both, and needle gunning seems to win. I’m sure there may still be times when blasting is the only workable approach, but as the alternatives improve, the justifications for blasting will have to be stronger and stronger to pass muster.
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