A hand-held concrete scarifier or milling machine used to remove or roughen concrete generates dust that may contain high levels of respirable silica.  An engineering control consisting of a hood and vacuum (a dust control system) that is designed to work with this equipment can reduce the amount of dust that becomes airborne and the risk of exposing the worker using the equipment and those working nearby to hazardous levels of silica dust.

This dust control system consists of a vacuum with a disposable filter (a high efficiency particulate air, HEPA, filter is recommended when practical) attached to a hood (or shroud) surrounding the flails, heads or multi-tipped cutting wheels. When used according to manufacturer specifications, the vacuum draws dust from the heads, the point of dust generation, and transports it to the collection unit. Capturing dust containing silica near the point of generation and removing it from the work environment reduces the concentration in the worker's breathing zone.

Cyclonic pre-separators, either as an integral part of the vacuum or as a separate unit, should be used to collect the majority of the particles before they reach the filters. The use of a cyclonic pre-separator reduces the amount of dust that collects on the filter, which increases the useful life of expensive filters and helps to maintain the vacuum’s initial airflow rate. 

A concrete dust control system is recommended by OSHA and is commonly used in the form of a vacuum dust collector. These methods allow for the safe and efficient removal of most airborne dust particles that result from using scarifiers and milling machines. Using a cyclonic separator and a vacuum with filters greatly reduces the risk to operators and other workers on a site.

Price and equipment models are subject to change. Please contact the manufacturer for the latest information.

Pentek Roto-Peen Scaler

The Roto-Peen uses a rotating hub with an assortment of options for the cutting media. The hub has flaps, as opposed to a solid rotating head, that rotate within the shroud (each flap has tabs that act as the cutting head, which is what actually makes contact with the concrete). The Roto-Peen is compatible with the VAC-PAC or other high-capacity, industrial HEPA vacuum systems.

• Number of Tungsten Tabs: 4 tabs per flap with a total of 6 flaps  
• Maximum Hub Speed: 2,400 revolutions per minute
• Weight: 6.5 pounds
• Compressed Air Supply Requirements: 30 cubic feet per minute at 90 pounds per square inch
• Vacuum Take-off Diameter: 1.5 inches
• Unit requires 1/2-inch diameter air supply hose and an in-line Lubricator-Regulator-Filter
• Maximum Removal Rate: 40 – 50 square feet per hour
• Sound Pressure Level: Not available.  Please note OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA

Pentek Air-Powered VAC-PAC High Performance HEPA Vacuum Systems

• Maximum Static Pressure: 100 inches of water
• Primary coarse filters:
  • Eight inches in diameter
  • Two for Models 6, 9, 12 and 15 and three for Models 18, 21 and 24
  • Remove approximately 95 percent of 1 micron particles
• Secondary HEPA filter (2 square feet) removes 99.97 percent of 0.3 micron particles (the most penetrating size)
• Debris is deposited in a standard 55-gallon drum (23-gallon drums for use with 55-gallon overpacks are available)
• Features: automatic full-drum level alarm, connections for up to six hoses
• Weight: 750 pounds
• Automatic self-cleaning by reverse-flow pulses of high pressure air

Pentek Electric-Powered VAC-PAC High Performance HEPA Vacuum Systems

• 220 volt, three phase electric motor
• Primary coarse filters:
  • Eight inches in diameter
  • Two for Models 10 and 13 and three for Model 22
  • Remove approximately 95 percent of 1 micron particles
• Secondary HEPA filter (2 square feet) removes 99.97 percent of 0.3 micron particles (the most penetrating size)
• Debris is deposited in a standard 55-gallon drum (23-gallon drums for use with 55-gallon overpacks are available)
• Features: automatic full-drum level alarm, connections for up to six hoses (1.5 to 4 inches in diameter)
• Automatic self-cleaning by reverse-flow pulses of high pressure air

Smith Manufacturing Hand-Held Concrete Scarifiers
 

Smith Manufacturing converts hand held electric grinders to concrete millers by replacing the grinding head.

• 
  Vacuum Take-off Diameter: 1.5 inches
• Maximum Removal Rate: 600 linear feet per hour
• Removal Depth per Pass: 1/16 inch
• Power Requirements: 120 volts, 8.1 amps
• Sound Pressure Level: Not available.  Please note OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA.
   

CS Unitec's Trelawny™ Rotopeen™

Pullman-Ermator USA Single Phase Electric Dust Extractors

(Photo courtesy of Husqvarna AB Construction Division)

• Filtration: cyclonic separator, coarse filter and HEPA filter capable of removing 99.97% of 0.3 micron particles (the most penetrating size)
• Sound Pressure Level: 75 dBA or less (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)

Pullman-Ermator USA Three Phase Electric Dust Extractors

(Photo courtesy of Husqvarna AB Construction Division)

• Maximum Static Pressure: 110 inches of water
• Filtration: cyclonic separator, coarse filter and HEPA filter capable of removing 99.97% of 0.3 micron particles (the most penetrating size)
• Dust Collection: Longopac® bag system which uses a 70 foot long plastic tube that is divided and sealed at the desired length
• Sound Pressure Level: 75 dBA or less (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)

* Greater area allows more time between filter cleaning or replacement

Ermator USA Cyclonic Pre-Separators

(Photo courtesy of Husqvarna AB Construction Division)

• Removes approximately 90 percent of particulates and can be used with Pullman-Ermator or other dust extractors
• Dust collection: Longopac® bag system, which uses a 70 foot long plastic tube that is divided and sealed at the desired length

(Photo courtesy of Husqvarna AB Construction Division)

Vacuum dust control systems create a cleaner work environment, and increase 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.).

Other items that may impact productivity include the time spent changing vacuum bags, which will depend on the amount of cutting being done and the size of the vacuum bag or hopper, and the time it takes workers to adapt to working with a vacuum hose attached to the tool.

To achieve maximum dust control and exposure reductions, the saw and vacuum system must be maintained and the workers must be trained on the proper use of the equipment.  Use of tools and the tasks performed must also be in compliance with applicable local, state or federal regulations.   Things to consider:

• When dust is captured at the source, the risk of exposing other workers, members of the public, adjacent property, cars and building occupants is avoided, which reduces the risk of time consuming disputes and related liability.
• The vacuum must be located as close to the dust generation as possible to be effective. A hood or shroud is 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.
• Not all vacuums and filters are effective in reducing exposures.  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 very dusty jobs.
• For dust containing harmful particles like silica, it is important to use the highest efficiency filters as practical. The best available are called HEPA (High Efficiency Particle Air) filters because they capture 99.97% of 0.3 micron particles (the most penetrating size).  It is important to keep in mind that 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. For operations that generate large amounts of dust, a cyclonic collection unit may be the best solution. Cyclonic collection units spin the particles and drop them into a vacuum bag.  As a result, these units can be used with less expensive vacuum bags and the bags need to be replaced far less frequently because loading of the bags does not cause a pressure drop.  
• Large electric vacuums commonly require 20 amp electrical circuits in addition to the additional amp circuit used for the electric tools.  Cords and extensions must be rated for the tool's power requirements, be inspected regularly, and used in combination with ground fault interrupt circuits.
• Concrete scarifiers and millers can generate sound levels that are greater than 90 decibel.  When employees are subjected to sound levels exeeding 90dbA, feasible adminstrative or engineering controls for noise shall be utilized.

Andrew Kingston and Michael R. Cooper - Aria Environmental, Inc.
Bruce Lippy - CPWR

• Residential Construction
  • Perform surface grinding or cutting
    • Construction dust
    • Silica