Solution Summary: Hand-held Masonry Saws with Wet Dust Suppression
Cutting bricks, blocks, stone, concrete and other masonry materials generates a large amount of dust that may contain high levels of crystalline silica and create a hazard for everyone in the vicinity. Increasingly, nano-enabled masonry products are being used in construction that can also expose workers to inhaling engineered nanomaterials when the products are being cut, such as concrete roofing tiles that contain nano-size titanium dioxide for example. Wet dust suppression is a control option for hand-held masonry saws (also called “cut-off,” “chop,” and “concrete” saws). The size of the blades used with these saws varies depending on the manufacturer and model. While it is common to find them with blades ranging in size from 12 to 16 inches, there are versions with smaller blades. In general, this type of control uses a pump or line pressure to deliver water through a hose to the saw blade/cutting surface where it combines with particles and reduces airborne dust levels. Water can be supplied through a hose connected to a municipal water supply or from a portable water source.
The following are examples of commercially available saws with wet dust suppression systems:
Husqvarna Power Cutters with wet dust suppression
STIHL Cutquik® Cut-Off Machines with wet dust suppression
Stihl gasoline powered cut-off saws have blades ranging in size from 12- to 16-inches. These saws are are used to cut concrete, masonry, reinforced concrete, brick, natural stone, clay pipe and asphalt. For wet cutting, a standard hose, or optional pressurized water tank and hose, is connected to the water hose connection on the saw. The TS 410 A and 420 A models are equipped with an Electronic Water Control (EWC) that allows the user to control the flow of water to the cutting surface using a key pad on the saw. Click on the models below to learn more.
|Model||Cost||Max Blade Diameter, in||Max Cut Depth, in||Blade Speed, RPM||Power, HP||Weight, lbs|
|TS 410A (EWC)||$1,080||12||3.9||5,350||4.4||21.8|
|TS 420A (EWC)||$1,130||14||4.9||5,350||4.4||22.3|
- Light weight and balanced for less operator fatigue
- Best power-to-weight ratio in the industry
- Smooth start decompression valve reduces start up force by 70%
- 12" or 14" blade capacity models
- 5-stage filtration system
- Fully adjustable blade guard
- Water kit included with standard garden hose quick disconnect
- Powerful 73cc engine
|Model||Cost||Max Blade Diameter, in|
Husqvarna Power Cutters with wet dust suppression
(Photo courtesy of Husqvarna AB Construction Division)
Husqvarna offers several Power Cutters with blades ranging from 12- to 16-inches that can be used to cut concrete and masonry including pipes and window and door openings. For wet cutting, a standard hose, or optional pressurized water tank and hose, is connected to the water hose connection on the saw. The K 3000 Wet features an “integrated regulator that controls the water volume, ensuring a constant flow to the blade, and a Ground-Fault Circuit Interrupter." Click on the models below to learn more.
|Model||Cost||Max Blade Diameter, in||Max Cutting Depth, in||Power||Weight, lbs|
|K760 gas||$1,039||12,14||4, 5||5 HP||20.7, 21.6 excludes cut equipment|
|K970 gas||$1,389||12,14,16||4, 5, 6||6.5 HP||23.4, 24.3, 26.0 excludes cut equipment|
|K1260 gas||$1,649||14,16||5, 6||7.9 HP||30.2, 31.8|
|K3000 electric 120V||$909||12,14||3.94, 4.92||1800W||19.62 includes cut equipment|
Inhaling silica dust may cause silicosis or lung scarring with prolonged exposure. Silicosis is an incurable, sometimes fatal, disease. Exposure to silica also causes lung cancer and other lung diseases including chronic obstructive pulmonary disease (COPD) and tuberculosis, and has been linked to renal disease and rheumatoid arthritis. A report by OSHA noted that studies “show that using a handheld masonry saw to cut bricks, concrete blocks and similar materials can result in hazardous levels of airborne silica if measures are not taken to reduce dust emissions. Operating a handheld masonry saw outdoors without dust controls can produce silica exposures in excess of 14 times the Occupational Safety and Health Administration’s (OSHA) permissible exposure level (PEL) for respirable crystalline silica in construction of 50 ug/m3 (micrograms per cubic meter of air, which is the same as 0.05 mg/m3, milligrams per cubic meter) as an 8-hour time-weighted average (TWA), Short-term exposures or exposures from operating saws indoors can be significantly higher (up to 10 mg/m3).” (OSHA Controlling Silica Exposure in Construction – 2009)
There is no evidence yet that engineered nanomaterials have caused harm in exposed workers. However, it is most important that exposures be limited and that precautionary approaches be used to reduce exposure and protect construction workers from the potential hazards of engineered nanomaterials. Nano-size ultrafine titanium dioxide, which can be present in nano-enabled masonry products, has been found to cause inflammation of the lungs and lung cancer in lab animals. The National Institute for Occupational Safety and Health (NIOSH) has determined that ultrafine titanium dioxide should be considered a potential occupational carcinogen. Other engineered nanomaterials that may be present in nano-enabled construction materials used in masonry work could also have the potential to cause harm when inhaled. Cutting nano-enabled concrete roofing tiles without engineering controls can generate excessive amounts of airborne dust that if inhaled by workers could increase the risk of developing respiratory disease (West GH, et al 2016)
OSHA has no specific regulation or Permissible Exposure Limit (PEL) for any engineered nanomaterial. However, NIOSH has a recommended exposure limit (REL) for ultrafine titanium dioxide of 0.3 mg/m3 as a time-weighted average (TWA) concentration for up to 10 hours/day during a 40-hour week. The intent of the REL is to lower the risk to workers of the potential for developing lung cancer.
How Risks are Reduced:
When water is used to suppress dust or silica at or very near the source, dust concentrations in the worker’s breathing zone and exposures are reduced. In some cases, particularly where work is intermittent or in an area with general ventilation, use of water may be adequate to reduce the need to wear a respirator and the need for an employer’s respiratory protection program. Wet dust suppression is also likely to be effective in reducing concentrations of airborne engineered nanomaterials in a worker’s breathing zone.
For example: The 2009 OSHA report “Controlling Silica Exposures in Construction,” referenced a study that found “respirable dust levels were reduced by up to 94 percent for pressurized portable water supply systems and up to 96% for a constant supplying water source… [and] When effective wet methods are used outdoors, it is unlikely that supplemental respiratory protection will be needed.” (“Measurements of the effectiveness of dust control on cut-off saws used in the construction industry,” 1999 Thorpe, et.,al) The OSHA report also included NIOSH data that found “that an employee dry cutting on concrete outdoors was exposed to 1.5mg/m3 of silica as an 8-hour TWA [time-weighted-average]" and noted that “a reduction of 96% in respirable dust for this employee would have resulted in exposure around 0.06mg/m3 if the employee switched to wet methods.” In this example, wet methods would have dropped the workers exposure just above OSHA’s permissible exposure limit (PEL) of 0.05 mg/m3. The report also states that “Wet cutting, when used properly, is an effective way to reduce employee exposures to silica dust and in most cases maintains exposures below the allowable limit. Wet cutting is the most effective method for controlling silica dust generated during sawing because it controls the exposure at its source.”
In addition, a study of engineering controls, (In Depth Survey of Dust Control Technology for Cutting Concrete Block and Tuckpointing Brick, 2008, Echt et al.) observed an 88 percent reduction in respirable dust and a 90 percent reduction in respirable silica, compared to use of no control, during the use of a hand-held masonry saw with a water-spray attachment.
Husqvarna models use a DEX® dust management system for wet and dry cutting or a "water saving wet cutting kit, which efficiently binds dust with less water usage and slurry, compared to traditional wet cutting."
There are no reported studies specifically evaluating the effectiveness of wet dust suppression methods in controlling construction worker exposure to engineered nanomaterials in nano-enabled masonry products when using handheld masonry saws. However, because wet dust suppression methods with handheld masonry saws have been demonstrated to be very effective in reducing exposures to respirable dust and silica, it is expected that wet cutting will also be effective in reducing worker exposure to engineered nanomaterials as well.
Effects on Productivity:
Wet dust suppression increases workers’ visibility and comfort when engaged in dust producing tasks. Improved worker visibility and comfort may in turn result in less fatigue for the worker and greater productivity. Capturing dust at the source may also eliminate or reduce time spent cleaning up the work site and adjacent property (including cars, etc.).
To achieve maximum dust suppression and exposure reductions the equipment must be maintained and workers must be trained on the proper use of the equipment. Use of the tools and the tasks performed must also be in compliance with applicable local, state or federal regulations. Things to consider:
• “Concern that excess shrinkage as the units dry might lead to cracks has led some overly cautious specifiers to prohibit wet cutting. The bottom line is that the amount of water added to the unit during site cutting is insignificant, in terms of shrinkage. This was clarified in the ACI 530.01-05/ASCE6-05/TMS 602-05 Specification for Masonry Structures. The article on wetting concrete masonry units includes this sentence: “Wet cutting is permitted.” (Source: http://www.imiweb.org/imi_toolkit/pdf/ClarificationWetCutting.pdf)
• The use of water-based controls may result in wet and slippery ground and walking surfaces. During cold weather this may lead to the formation of ice and increase the risk of slips, trips and falls.
• Cutting debris that is not bagged and removed from the work area while wet may become airborne once dried, posing an inhalation hazard to anyone in the area. A work area free of debris and excess water must be maintained to reduce the risk of these hazards.
• The use of water as a dust control increases the risk of shock when electricity is used in the same area. Electrical cords and extensions must be rated for the tool's power requirements, be regularly inspected, replaced when damaged, and used in combination with ground fault interrupt circuits.
• The use of gasoline-powered equipment poses the risk of carbon monoxide exposure, particularly in areas where airflow is reduced. Small, inexpensive personal monitors can be worn by the operator to warn of unacceptable exposures. Gasoline powered equipment should not be used in confined spaces or indoors.
• Hand-held masonry saws frequently generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), which are hazardous. Hearing protection should be worn when using masonry saws unless an industrial hygienist has conducted noise monitoring and indicated that hearing protection is not required.
• Hand-held masonry saws frequently weigh more than 20 pounds and the heaviest exceed 30 pounds. Use of these tools will require a strong static effort which can lead to fatigue, pain and musculoskeletal disorders. Operators should take breaks on a regular basis and when fatigued. Consider having each tool and task combination evaluated by an industrial hygienist or ergonomist.
Bruce Lippy, PhD, CIH - CPWR - The Center for Construction Research and Training
Michael R. Cooper - Aria Environmental, Inc.
Bill Kojola, MS
Husqvarna K760/K970/K1260/K3000 Power Cutters with water connection
To obtain information, visit http://www.husqvarna.com or contact 1-800-700-5919 http://www.husqvarna.com/us/construction/company/contact-husqvarna/customer-service/
STIHL TS410/TS410A/TS420/TS420A/TS700/TS800 Professional Cut-Off Machines
To obtain information, visit http://www.stihlusa.com or contact 1-800-467-8445 http://www.stihlusa.com/products/cut-off-machines/professional-cut-off-machines/