Cutting concrete and other masonry materials generates a large amount of dust which may contain high levels of crystalline silica and creates a hazard for everyone in the vicinity. Vacuum dust controls exist for gas and electric walk-behind masonry saws. These controls consist of a vacuum, with a disposable filter (a high efficiency particulate air, HEPA, filter is often an option and recommended where practical), attached to a shroud that is compatible with the saw and partially encloses the blade. The vacuum draws air and dust from the blade, the point of dust generation, into the shroud where it is transported through tubing and into the vacuum's bag or reservoir.

EDCO, Inc. 14-inch upcut Walk-Behind Masonry Saws with Edco Vortex 290 vacuum

 

• Used for expansion joint cleaning, green concrete cutting, slab cutting, contraction joints, patch repairs in asphalt, traffic loop installation and trenching
• Vac Port Blade Guard ($353) is required for use with vacuum
• Blade diameter: 14 inches
• Maximum cutting depth: 4 ¾ inches
• Alternative dust control: hose connection for wet cutting
• Sound pressure level: greater than 85 dBA and likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)
• Dust capacity: 9 gallons
• Filtration: main filter removes approximately 98 percent of particles; HEPA filter kit can be purchased for approximately $1,400

Models	Costs	Power Requirements	Horsepower	Unloaded Blade Speed, RPM	Weight, pounds
SB-14-9H	$3,164	Gasoline	9	3,600	170
SB-14-11H	$3,463	Gasoline	11	3,600	193
SB-14-13H	$3,494	Gasoline	13	3,600	193
SB-14-5B	$3,263	230 volts, single phase, 19.5 amps or 230/460 volts, three phase, 12/6 amps	5	3,450	205
ASB-14	$2,836	air, 160 ft3/min at 90 lb/in2	5	2,500	16

 

Vacuum dust control systems can have either positive or negative effects on productivity. However since use of vacuums eliminates large amounts of both airborne and settled dust, they provide a cleaner, more efficient means of masonry cutting.

Improved visibility can improve quality and productivity. Dust capture greatly reduces site cleanup times. Dust capture avoids exposing other workers, members of the public, adjacent property, cars and building occupants, which can be associated with increased liability and time consuming disputes. Improved worker comfort is a result of reduced dust which may in turn result in less fatigue for the worker and greater productivity. In some cases, particularly where saw use is intermittent, vacuum dust control may be adequate to reduce the need to wear a respirator, and the need for an employer respiratory protection program.

Some additional issues should be considered. Changing vacuum bags takes time, which will depend on the amount of cutting being done and the size of the vacuum bag or hopper. Workers will need to adapt to working with a vacuum hose attached to the tool. Saw and vacuum energy requirements may exceed the capacity of a single standard 20 Amp circuit when combined requiring access to two circuits or special wiring.

• The vacuum must be located as close to the dust generation as possible to be effective. A shroud may be needed to contain the dust so the vacuum can capture it. The shroud must be kept as close to the work surface as is practical to provide adequate dust capture.
• The particles that can do the most damage in the lungs are small enough to penetrate the filters found on many shop vacuums. Additionally, some inexpensive shop vacuums pull the dust through the motors, which can destroy the vacuum on really dusty jobs, eliminating any initial cost savings.
• For dust containing harmful particles like silica, it is important to use as high efficiency filters as practical. The best available are called HEPA (High Efficiency Particle Air) filters because they capture 99.97% of the most penetrating particles. But HEPA filters also create a greater pressure drop and decrease in air flow rate because it is more difficult to pull air through these denser filters so capture velocity may be reduced. They also require pre-filters to extend the life of the HEPA filters, which are more expensive than other filters. Studies have shown that it may be more effective to direct the exhaust air out of the work area than to attempt to add HEPA filtration for a tool where it isn't an integral part already. HEPAs require routine disposal of prefilters, which can cause exposures to those doing the filter change out.
• For operations that generate large amounts of dust, cyclonic collection units, if available, may be the best solution. Rather than require more expensive filters and bags that must be frequently changed, cyclonic units spin the particles and drop them into cheap bags that need to be replaced far less frequently because loading of the bags does not cause a pressure drop.
• Vacuum performance must be monitored on a regular basis. For high dust generating tasks, dust caked on the filter may reduce flow to a level where it no longer provides adequate dust capture. Automatic and manual filter shakers, coarse pre-filters and cyclonic collections units are available with some vacuums and may help maintain the air flow rate.

Large electric vacuums commonly require 20 amp electrical circuits in addition to the 20 amp circuit used for the electric masonry saw.  Cords and extensions must be rated for the tool's power requirements, be inspected regularly, 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. Steps to control exposure are important because the gas is invisible, odorless and tasteless. Small, inexpensive personal monitors can be worn by the operator to warn of unacceptable exposures.

Walk-behind masonry saws frequently generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), and 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.

As is the case with any construction equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.  Many cities have ordinances that prohibit release of visible dust as a public nuisance.  Vacuum dust collection systems may provide a mechanism for compliance.

Bruce Lippy, PhD, CIH - CPWR - The Center for Construction Research and Training
Michael R. Cooper - Aria Environmental, Inc.
Bill Kojola, MS