Vacuum Blasting

Using vacuum blasting equipment can help reduce exposure to silica, lead, and other hazardous substances produced by the abrasive blasting process.

Description:

Abrasive blasting (also known as sandblasting) is a process commonly used to remove coatings or add texture to a metal or concrete surface. It involves shooting a pressurized stream of abrasive material against the surface until the desired effect is achieved.  There are a wide variety of abrasive materials (blasting media) that can be used, including silica sand, coal slag, steel shot and grit, and milder media like walnut shells, dry ice, baking soda, and sponges.  Depending on the media, blast pressure, paints or coatings, base material, and control methods, abrasive blasting can create large clouds of dust that contain extremely high concentrations of silica, lead, and other hazardous substances.
 
Vacuum blasting is a self-contained abrasive blasting process that recaptures both the blasting media and the particles released from the base material at the point of contact.  This process uses one nozzle held flush against the blasting surface to direct and apply the blasting media and also to collect dust, particulate, used media, and other waste products resulting from the blast.
 

Vacuum blasting is also referred to as “dustless blasting” or “closed-loop abrasive blasting.”  Because it does not produce a dust cloud when used as recommended, it is ideal for use in confined spaces and on hazardous materials like surfaces coated with lead-based paint.  Some vacuum blasting units are designed to filter dust and dislodged particles from the blasting media and route the recycled abrasive back to the blast pot so it can be reused multiple times.

 

Figure 1. The Vacuum Blasting Process

 

 

There are many different types of vacuum blasting systems designed for a variety of applications.  These include:

 

Nederman SB750 Suction Blaster: 

Courtesy of Nederman Corporation
  • Base Price: $1,501 (verified 1/24/19)
  • Portable
  • Light duty
  • Requires connection to air compressor

 

 

NovaTek Contained Blast System:

Image provided by NovatekCo
  • Base Price: $10,799 (verified 1/24/19)
  • Metal drums not included

Risks Addressed:

Abrasive blasting creates large amounts of dust.  The amount and composition of the dust generated varies depending on a number of factors such as:
 
  • the type of surface (substrate) being cleaned (eg. masonry, steel, or concrete)
  • the type of blasting media
  • the thickness and type of paint or coating being removed
  • the amount of air pressure being used
  • the control methods being utilized 
 
Hazardous amounts of silica are often present, especially when the blasting media is silica sand.  Uncontrolled blasting with silica sand can produce up to 27,000 ug/m3 of respirable crystalline silica, about 540 times higher than OSHA’s permissible exposure limit (PEL) (Jennison & Cocalis, 1995).  When abrasive blasting is used to remove paints or coatings, it can create clouds of suspended paint particles.  If this paint contains lead, inhaling it can cause lead poisoning. Uncontrolled blasting with steel grit on a bridge covered in lead-containing paint produced up to 14,000 ug/m3 of airborne lead (Mickelsen & Froehlich, 1993; Virji, Woskie & Pepper, 2009).  This is about 280 times higher than OSHA’s lead PEL.
 
In addition to the health hazards to workers, uncontrolled blasting also creates health hazards for people who live and work in the surrounding community.  Lead-containing paint dust that falls to the ground is absorbed into the soil and can move into local waterways, contaminating the local water supply.  Young children are especially susceptible to lead poisoning, and may ingest contaminated soil while playing outside or from dirt tracked indoors on shoes. 
 
Depending on the substrate as well as the coatings being removed, the waste generated by abrasive blasting may also include radioactive contamination and PCBs. 

How Risks are Reduced:

Vacuum blasting captures dust and particles created by the abrasive blasting process at the point of generation, preventing them from being discharged into the environment and protecting both workers and the local community.  Some vacuum blasting systems also use a closed circuit design to separate and recycle the spent abrasive. This reduces the likelihood of inhaling or coming in contact with hazardous substances while collecting, cleaning, and separating blasting media reclaimed from the environment.

Effects on Productivity:

Because local exhaust ventilation is integrated into the vacuum blasting unit, there is no separate equipment to purchase and maintain. There is also no need to spend time or resources collecting the spent blasting media.  Closed-loop vacuum blasting systems that filter and recycle spent media save time, labor, and the cost of cleanup and new abrasive media purchase.  
 
Although the size of a vacuum blasting nozzle is usually smaller than the surface area of an open blast, vacuum blasting creates more uniform surface etching.  Using a vacuum blasting system can also prevent wear and tear on machinery or electronics on the blast site by preventing clogging or interference from dust. This can save both labor and maintenance costs.

Additional Considerations:

If vacuum blasting is not practical, consider using a wet blasting (vapor blasting) technique to minimize dust generation.  You can also switch to a safer abrasive material, for example, by using steel shot and grit instead of silica sand.  The use of a blasting cabinet or enclosure can help isolate workers from hazardous substances.  Laser surface cleaning can also be used for especially delicate substrates, and latex strippers will remove surface coatings while preventing release into the environment.

When performing abrasive blasting of any kind, use a Type CE NIOSH-certified blasting airline respirator with positive pressure blasting helmet.  Abrasive blasting is also an extremely loud activity.  OSHA requires that workers wear hearing protection sufficient to keep their 8-hour average noise exposure (LAeq) under 90 decibels, and NIOSH recommends maintaining it under 85 decibels.

Contributors:

Sara Brooks, MPH, CPH: CPWR - The Center for Construction Research and Training
Bruce Lippy, Ph.D., CIH, CSP, FAIHA: CPWR - The Center for Construction Research and Training
Mike Kassman, MAHP, CHST, PA-AIC, APT: CPWR - The Center for Construction Research and Training

Hazards Addressed: