Removing, roughening or resurfacing concrete with a hand-held scabbler generates a large amount of dust that may contain high levels of crystalline silica or other hazardous materials and creates a hazard for everyone in the vicinity.  Vacuum dust controls are available for concrete scabblers.

These controls consist of a vacuum with a disposable filter (a high efficiency particulate air, HEPA, filter is recommended when practical) attached to a shroud surrounding head or hammer. The vacuum draws air and dust from the head, the point of dust generation, and transports it to the dust collection unit. Capturing dust and 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 capture and control system is recommended by OSHA and is commonly used in the form of a vacuum dust collector. These methods allow for the safe removal of most airborne dust particles that result from scabbling. Using a cyclonic separator and a vacuum with filters greatly reduces the risk to operators and other workers on a site.

CS Unitec's Trelawny™ Pneumatic Heavy-Duty Hand-Held Scabblers

* cubic feet per minute at 90 pounds per square inch
** 90 dBA is OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average
*** 4 hours is ACGIH’s Threshold Limit Value (TLV) for exposure to 6 meters per second squared (m/s²) hand vibration and 2 hours is the TLV for exposure to 8 (m/s²).

These CS Unitec scabblers with vacuum shrouds are compatible with the CS Unitec vacuum systems.

CS Unitec, Inc. Vacuums: CS 1225, CS 1435, and CS 1500

• Air flow rate: 130 cubic feet per minute
• Water lift: 98 inches
• Available bags:
  • Plastic is ideal for concrete dust
  • Paper is ideal for general debris
  • Water permeable is ideal for concrete slurry
• Power requirements: 120 volts, 11 amps
• Filtration: standard filter removes 99.93 percent of 3.0 micron particles, optional HEPA filter removes 99.97 percent of 0.3 micron particles (the most penetrating size)
• Filter area: standard filters are 9.25 square feet (greater area allows more time between filter cleaning or replacement)
• Automatic electromagnetic pulse filter cleaning system to maintain performance

Pentek Squirrel-I Scabbler

The Squirrel-I is compatible with the VAC-PAC vacuum systems.

• Points per Head: 9 made of tungsten carbide
• Weight: 40 pounds
• Compressed Air Supply Requirements: 25-30 cubic feet per minute at 90 pounds per square inch
• Vacuum Take-off Diameter: 1.5 inches
• Maximum Removal Rate: 25 – 30 square feet per hour
• Removal Depth per Pass: 1/8 – ¼ inch
• Sound Pressure Level: not available but likely to exceed 90 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average)

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

* cubic feet per minute at 85 pounds per square inch

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

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 collectors are expected to have a positive effect on productivity and improve the quality of the work by removing large amounts of dust, which provides a cleaner environment for operators and reduces the effort and time required for clean-up.  Dust capture avoids exposing other workers, members of the public, adjacent property, cars and building occupants, which can increase liability and time-consuming disputes.  Improved worker comfort is a result of reduced airborne dust which may in turn result in less fatigue for the worker and greater productivity.  In some cases, particularly where work is intermittent or in an area with general ventilation, use of dust collectors may be adequate to reduce the need to wear a respirator, and the need for an employer’s respiratory protection program. 

Some additional issues should be considered.  Changing vacuum bags takes time, which will depend on the amount of scabbling 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. 

Ventilation for construction tools is often misunderstood. These are some key concepts that can help:

• The vacuum must be located as close to the dust generation as possible to be effective.  A 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.
• 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 0.3 micron particles (the most penetrating size).  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.
• 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 plastic bags.  The plastic bags are less expensive than many vacuum bags and the bags 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 collection units are available with some vacuums and may help maintain the air flow rate.

Large electric vacuums commonly require electrical circuits that can provide greater than 20 amps and/or more than 120 volts.  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 diesel and particularly gasoline-powered compressors and equipment poses the risk of carbon monoxide exposure, especially in areas where airflow is reduced.  Steps to control exposure are important because the gas is invisible, odorless and tasteless.  Poisoning by carbon monoxide can occur quickly indoors, but working outdoors does not ensure operators won’t be overcome.  Small, inexpensive personal monitors should be worn by the operator to warn of unacceptable exposures.  Equipment should not be left idling to cut down on carbon monoxide and to conserve fuel.

Concrete scabblers can generate sound levels that are greater than 90 decibels, the OSHA Permissible Exposure Limit (PEL), and hazardous.  Hearing protection should be worn when using concrete scabblers 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.