How Concrete Cutting Tools Answer the OSHA Silica Standard
We tried out concrete and masonry cutting systems from several brands in accordance with Table 1 compliance of the new OSHA construction standard.
By Michael Springer
By now, anyone who cuts or drills into concrete or masonry knows that the new Occupational Safety and Health Administration (OSHA) standard has changed the way this work must be done since, at the time this article was written, it was set to go into effect Sept. 23. Extra steps must be taken to deal with the dust created when working with these materials. These steps include writing plans, keeping records, and using specified tool attachments, and/or air quality monitoring of the jobsite and medical surveillance of workers. To help our readers better understand these new requirements, I surveyed concrete-cutting systems from several tool brands and used them in compliance with both the OSHA regulations and the manufacturer’s instructions (required by OSHA as well). During this process, I tested six saws and grinders along with their mandatory dust-collection shrouds, and six dust-collection vacuums. I also performed wet cutting as is required for compliant use of one of the tools.
The OSHA Silica Standard
OSHA’s silica standard aims to limit worker exposure to respirable crystalline silica, which is known to cause silicosis, lung cancer, chronic obstructive pulmonary disease, and kidney disease. And it’s a goal that can’t be achieved by putting the burden on employees to simply wear respiratory protective equipment all of the time. The rules are far reaching, with comprehensive guidelines for all industries that deal with this material hazard.
We focused solely on the section that applies to construction work, which is OSHA standard 1926.1153. It applies to all work during which employee exposure may be at or above the action level of 25 micrograms per cubic meter of air (25 µg/m3 ), averaged over an eight-hour day. The standard is not simply a set of guidelines or recommended practices; it’s a law, so it will have to be followed by all employees and employers. Failure to comply can result in fines being levied against contractors and subcontractors alike, and can cause projects to be shut down.
There are two basic ways to work within the rules. An employer can choose to take responsibility for assessing the exposure of each employee by sampling and analyzing the air quality at a worker’s area and/or by providing objective data to prove the work methods keep the silica dust below the permissible exposure limit (PEL) of 50 µg/m3, averaged over an eight-hour workday. Or, an employer can choose to follow specified exposure control methods detailed within the OSHA standard in a document called Table 1, which can be viewed at osha.gov/silica/Table1sect1926.1153.pdf.
The second option is designed to be the easier route to follow for dusty tasks, since it relies on buying the appropriate hardware and using it as directed versus dealing with the hard science of determining actual exposure levels of respirable crystalline silica on the job. Employers who follow Table 1 correctly do not need to measure for worker exposure and do not need to worry about the PEL. However, it’s not quite as simple as just abiding by the specified control methods. You can read more about your responsibilities if you employ workers at osha.gov/Publications/OSHA3681.pdf.
Following Table 1
In general, if you follow the Table 1 methods correctly, you should be assured of compliance with the standard. But if you don’t adhere to the rules exactly, you must also follow the alternative control methods that rely on air quality monitoring and/or other sources of objective data.
Note the importance of owner manuals for using Table 1 as your exposure control method. If you find a situation where instructions in a tool’s owner manual contradict the OSHA standard, you are expected to follow the more stringent or conservative directions. Most tool and equipment manuals can be found online on manufacturers’ websites, so you should be able to read through them beforehand.
Concrete cutting with saws and grinders
While using the various concrete cutting tools in the test, I followed item 2 (ii) in the table for saws, and item 12 (xii) for grinders. For Table 1 compliance, tools categorized as saws can only be used wet, whether indoors or outdoors, while tools categorized as grinders can be used wet outdoors or dry both indoors and outdoors. I say “categorized as” because some companies want the option to interpret their saw-like cutting tools as grinders for the purpose of being used for dry cutting within Table 1 of the OSHA standard.
As seen in the table, cutting with a saw requires the tool to be used with an attached device to apply water to the blade at a flow rate “sufficient to minimize release of visible dust” as further specified by OSHA. For any work indoors, or for use outdoors longer than four hours, a specified class of dust-mask or half-face respirator must be used. To clarify, as soon as the duration of work is known to be exceeding four hours, the respiratory protection must be put on.
For general cutting and grinding work with grinders, wet work can be done with the same requirements as saws for outdoor jobs, but with no respiratory protective gear required. For work performed dry, respiratory gear is needed only for jobs lasting four hours or longer when indoors. But some special hardware is required for dry use, including a manufactured dust shroud fitted to the tool and connected to a vac with suitable airflow and a filter rated at 99 percent efficiency or higher. The vac must have a built-in mechanism to clear the filter of excess dust or be used with a cyclonic separator instead. I’m a big fan of cyclonic separators and I always use one in the shop, but it’s an extra piece of equipment to lug around on site. So, I chose vacs that were ready to go off the shelf with compliance features built in.
It’s not a requirement of OSHA, but I used tool, shroud and vac systems all from the same brand. This assured me that the components would all fit together and that they were approved for Table 1 compliance as a system. It’s also not a requirement of OSHA to use a HEPA filter in a vacuum used to collect dust while connected directly to a tool, but I swapped some stock filters out for HEPA filters to provide for compliant cleanup work using the same vacs.
Work site cleanup
Known as “housekeeping” in OSHA’s terms, the cleanup of materials containing silica dust has some specific rules of its own. But some confusion is caused by certain cleanup rules that seem contrary or are left vague. Dry sweeping and dry brushing to clean up dust are not generally permitted, nor is blowing any dust around with compressed air. Instead, picking up settled dust with a vac equipped with a HEPA filter is the rule for dry cleanup. Perhaps the same dust at different times represents a similar exposure hazard to workers, but the standard was written with the need for two different grades of filters for this work. As it is, with a Table 1-compliant vac filter you can’t disconnect the hose from the tool to pick up any dust around where you are working without first upgrading to a HEPA filter. In light of this literal “double standard,” it only makes sense to install a HEPA filter in your vac, so you can use one vac for both uses on the job. Good paper or fabric filter bags will keep almost all of the dust and debris from reaching the filter and greatly prolong its useful life.
Wet cleanup methods also may be employed with wet sweeping of the slurry or by collecting it with a wet vac fitted with an appropriate filter. Wet liner bags may be of the waterproof type that requires you to lift the weight of all the water and mineral sludge up out of the vac. Or, they may be the fabric filtering type that allows you to dump or drain the water out of the vac canister separately from the solid contents contained in the bag. A vac with a drain port or hose at its lowest point is the type to use for this second wet disposal scenario.
The OSHA standard conspicuously lacks recommendations for what to do when it’s time to empty your vac, whether wet or dry. Concerns such as what type of liner or filter bag to use in a vac for efficient collection, containment, and disposal may be outlined in the vac’s manual, but the manner of disposal is left for the employer to figure out. State or local environmental regulations may be the final word in determining if the waste materials can be disposed of on site and any water dumped may have to be pH neutralized first.
In any case, cleanup and disposal methods should follow the employer’s required written plan and must avoid exposing any worker above the PEL while performing or in close proximity to any of these operations. This should include any nearby workers who are employees of other companies present on the jobsite as well.
I used handheld concrete cutting tool systems from six major brands: five grinder-type cutters designed for dry use only, and one saw made to be used either wet or dry.
The four small grinders cut to a maximum depth of about 1 inch for thin CMUs and expansion joints in concrete. These are more difficult to hold perpendicular to a slab than larger cutters, but their freehand abilities make them the go-to tools for crack chasing, concrete repair, and tuckpointing. The large grinder-type cutter reached deep enough to cut through residential slabs nearly 5 inches thick, and the lone saw in the test worked well for cutting straight lines up to 2 inches deep.
Bosch – GWS13-50VS grinder with GA50DC shroud and VAC090A vac.
Specs: 5-inch grinder, 13 amp, variable speed up to 11,500 rpm, lock-on slider switch, electronic clutch. Shroud shoe raised up on wheels, multiple depth stop settings (in metric units), and nice angled vac port. 9-gallon wet/dry vac, 150 cfm, switched automatic filter cleaning mechanism, 9.5 amps, variable speed, tool-activated outlet, comes with single 99 percent or better filter, HEPA filter available.
Pros: Filter cleaning feature of vac can be turned off for improved dust collection
Cons: Wheeled shoe provides a gap for dust to escape.
DeWalt – DWE46103 cutting tool with shroud and DWV012 vac.
Specs: 5- or 6-inch grinder, 13 amp, 9,000 rpm, lock-on slider switch, electronic clutch, soft-start. Shroud has mostly open design, pivoting foot for setting depth, all steel construction. 10-gallon wet/dry vac, 155 cfm, full-time automatic filter cleaning mechanism, 11.6 amps, variable speed, tool-activated outlet, comes with dual HEPA filters.
Pros: Door on shroud can be hinged open for closer access to corners, open-sided designs allows very good visibility of cut, steel shroud sturdier than other designs
Cons: Open shroud lets a lot of dust escape at times and seems to be made for tuckpointing only and not cutting; lack of a shoe makes it difficult to hold tool perpendicular to work surface; lack of a sight on front of the shroud makes it difficult to cut along a marked line; filter cleaning feature of vac can’t be turned off to improve dust collection.
Hilti – DCH300 cutting tool with 212131 shroud and VC300-17X vac.
Specs: 12-inch cutter with large grinder motor, 20 amp, 4,900 rpm, non-locking trigger switch, soft-start. Shroud fully enclosed and shoe sits tight against cutting surface, spring-loaded shroud can plunge cut down to depth stop setting up to 43⁄4 inches. 17-gallon wet/dry vac, 314 cfm, switched automatic filter cleaning mechanism, 17.5 amps, water drain hose, comes with single 99 percent or better filter, HEPA filter available.
Pros: Deepest cutting, handles slab and cut-off work others can’t; filter cleaning feature of vac can be turned off for improved dust collection; retractable shroud provides good dust collection, even when plunge cutting
Cons: Heavy machines—cutting tool over 20 pounds and vac over 60 pounds (when empty).
Makita – GA5040X1 grinder with shroud and XCV04Z and VC4710 vacs.
Specs: 5-inch grinder, 10 amp, 11,000 rpm, lock-on slider switch, internal suspension to reduce vibration. Shroud fully enclosed, large shoe sits tight against cutting surface, spring-loaded shroud can plunge cut to a depth stop, grinder handle attaches to shroud for better balance. (XCV04) 2.1-gallon dry vac, 127 cfm, automatic filter cleaning mechanism (cycles once when turned on or off), 9.2 amps, variable speed, comes with single 99 percent or better filter, HEPA filter available. (VC7410) 12-gallon wet/dry vac, 135 cfm, full-time automatic filter cleaning mechanism, 12 amps, variable speed, tool-activated outlet, comes with dual 99 percent or better filters, HEPA filters available.
Pros: Grinder felt stronger than the others when slowed by stones in the concrete and extra force had to be applied; side handle attachment point on the shroud aids the ergonomics of pushing or pulling the tool forward; small XCV04 vac can be run on two 18-volt battery packs for greater portability for cleanup uses (must be plugged in to achieve airflow required when connected to grinder though)
Cons: Grinder is the only one without a safety switch – if plugged in with the switch locked on, the tool will start; shroud leaves a thin line of dust to the right of the shoe that requires extra cleanup after cutting; filter cleaning feature of VC7410 vac can’t be turned off to improve dust collection. Small capacity of XCV04 vac requires more frequent emptying, and the lack of enclosed filter bags makes this a messy job as the loose filter has to be lifted out of the dust packed around it in the open canister, creating more worker exposure to dust than other vacs.
Milwaukee – 2780-22 grinder with 49-40-6110 shroud and 8960-20 vac.
Specs: 41⁄2- or 5-inch grinder, 18-volt cordless, brushless motor, 8,500 rpm, non-locking paddle switch, filter screens for motor vent. Shroud with closed shoe design, pivoting shoe for setting depth. 8-gallon wet/dry vac, 148 cfm, switched automatic filter cleaning mechanism, 7.4 amps, variable speed, tool-activated outlet, comes with dual filters, final stage is HEPA.
Pros: Very good dust collection overall. Cordless grinder offers a little more portability, but is still tethered to a hose; filter cleaning feature of vac can be turned off for improved dust collection.
Cons: Cordless tool had weaker sustained cutting abilities than corded tools, making 1-inch deep cuts less than 10 feet long on a battery charge, and usually overheating the battery pack at the halfway point; swapping the grinder out for one of the brand’s corded models would be much more productive for prolonged cutting, especially one with a lock-on switch instead of a paddle switch that must always be squeezed.
Skilsaw – SPT79 Medusaw.
Specs: 7-inch worm-drive circular saw, 15 amp, 5,100 rpm, non-locking trigger switch. Shroud is upper wheel guard, shoe raised up on wheels, spring-loaded mechanism lets saw plunge cut down to depth stop setting up to 2 inches. Vac port vented through the front handle for dry sawing, supplied water hose attachment for wet cutting.
Pros: This saw cut much faster and easier wet than dry, with less vibration and excellent dust control; tracks very straight in cuts, and four sighting points located on the saw are helpful for following a line
Cons: Dry use of saws not covered in Table 1 so alternative exposure control methods would have to be followed to saw dry; dry cutting according to the manufacturer’s instructions and with the saw attached to a compliant vac is slow and lets a lot of dust get by; play in the spring-loaded depth stop catch causes extra vibration during cutting sometimes which requires excessive downward pressure on the rear handle to stop, which is uncomfortable
Results and recommendations
After putting some hours on all of the tools – mostly cutting thick, aged concrete – I came up with a few conclusions for getting the most effective dust collection while cutting.
– Filter cleaning mechanisms should be turned off if possible while cutting. Every time a vac momentarily cuts suction to let the filter drop dust, there is a usually a corresponding puff of dust seen escaping the tool shroud. The rules require the vac to have a filter-clearing mechanism but do not speak to its use, so I recommend manually switching on the cleaning mode every few minutes while no dust is being sucked up. With the use of a good paper or fleece filter bag, vac filters stay clean enough without a constant cleaning cycle.
– A tight seal against the material being cut is important. A shoe that sits tight against the concrete leaks less dust than one spaced up on wheels. Gaps in the side of the shrouds made much less of a difference for dust collection, though.
– It’s much easier to collect the dust from a cut made in one full-depth pass versus making a series of cuts through the same kerf.
– Some dust will always escape with dry cutting. Every cutter shot, a visible trail of dust out the kerf several feet behind the tool, and any time a cutting wheel broke through the back side of a slab, half of the dust could no longer be collected by the shroud and vac. The same is true for all but the slowest plunge cuts, which must always be tilted down from the front of the shoe. Using a separate vac targeted toward these sources of dust would be the surest way to collect the most dust while cutting indoors. While not always as convenient to perform or clean up, wet cutting seemed to be more of a sure thing for knocking down dust while cutting.
Michael Springer is a tool tester and tool industry journalist in Boulder County, Colo.