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The issue of crystalline silica dust and the associated health risk to workers has been talked about for some time now, and previously published guidelines were no longer adequate to address modern dust levels and complexities present on many  New Zealand construction sites.


WorkSafe has now updated these guidelines, in particular clarifying the level of control methods and dust extraction specifications expected for workers working with Respirable Crystalline Silica (RCS) dust.

Silica is a natural substance found in concrete, bricks, rocks, stone (including artificial or engineered stone found in composite kitchen benchtops), sand and clay. RCS dust is created when materials containing silica are cut, ground, drilled, sanded, polished or otherwise disturbed. Silicosis is a progressive and deadly disease that causes fibrosis of the lungs from the inhalation of RCS dust.

The guidelines, ‘Silica Dust in the Workplace’, and ‘Controlling Dust with on-tool extraction’ were published in November last year and provide very clear topics that need to be addressed by persons conducting a business or undertaking (PCBU’s) in construction environments where dust is created by tools drilling, grinding, cutting, sanding etc., and also reinforces terminology that many tradespeople may still not be familiar with:

DUST EXTRACTION UNIT
When working with a known hazardous dust, tradespeople are expected to select a certified dust extractor (vacuum cleaner) that has been tested and approved at the design/manufacturing stage to perform to a certain certified level. Entry level vacuums, where the actual level of dust collection, filtration, and leakage cannot be verified, are therefore discouraged. This is especially the case when the often-cited concept of installing a ‘HEPA’ filter into a non-certified vacuum is incorrectly thought of as an adequate solution. HEPA is a vague and inaccurate terminology in the field of dust extractors and could mean that as much as 15% of fine dust particles pass through the filter straight back into the atmosphere, as well as much more dust leaking through inadequate seals and containment areas in these non-certified machines.

The required level depends on the hazardous nature of the dust being created, as identified by the building material’s manufacturer.

The International identification system of Low (L), Medium (M), or Hazardous/High (H) is used to identify both the risk presented by the dust, and the solution provided by the dust extractor, and is defined by Australian/New Zealand Safety Standards.

SELECTING/USING TOOLS THAT PROVIDE LOCAL EXHAUST VENTILATION (LEV) 
What the industry would commonly think of as a ‘dust port’ can be a standard feature of the tool, an optional accessory, or an aftermarket adaptor – a properly designed way of channelling the dust produced by each tool.

INTERCONNECTING HOSE SYSTEMS
International best practice already dictates that tools that produce the dust, and the dust extractors that collect the dust, can be professionally and efficiently interconnected with proper hoses and fittings, even when the brands of tool/extractor differ. These new guidelines encourage this best practice to become more prevalent on NZ construction sites.

MAINTENANCE AND TRAINING
Correct maintenance and operator training form important aspects of the PCBU’s responsibility to eliminate or reduce the level of construction site dust. Operator training, regular maintenance and testing, as well as safe storage and transportation, are all elements that PCBU’s need to ensure they have in place to ensure the chosen control measures are being used correctly and effectively.

Nilfisk can provide a fully compliant portable worksite dust extraction solution, as well as additional support in the form of customised vacuum hose and power tool integration, while a range of dust filtration and disposal methods are available 
to ensure safe, clean handling of construction site dust from the moment the dust is created, through to its final disposal. Fully automatic filter cleaning, in the form of Nilfisk’s INFINICLEAN system, electronic air flow monitoring, audible alarms, and innovative tool storage systems allow PCBU’s to embrace best practice when it comes to ensuring cleaner air quality and improved safety for workers.

For working with respirable silica dust, WorkSafe guidelines stipulate the use of a Certified H Class Dust Extractor/Vacuum Cleaner solution. An H Class Certified Vacuum is designed and certified to contain greater than 99.995% of the dust it collects, and is the only performance level accepted by WorkSafe to safely capture the minute particle size of the RCS dust.

For more information go to: https://worksafe. govt.nz/topic-and-industry/dust/controlling-dust-with-on-tool-extraction/ or https://worksafe.govt.nz/topic-and-industry/dust/silica-dust-in-the-workplace/