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What are Air Duct Cleaning Engineering Controls?

Posted by Peter Haugen on Thu, Dec 17, 2015 @ 10:00 AM

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Engineering controls are methods used to ensure worker and building occupant safety/health and to prevent cross-contamination during HVAC cleaning and restoration activities. Some of these methods include:

  • Source control/Zoning off
  • Isolation barriers/Containment
  • Pressure differential
  • Dust suppression
  • HEPA vacuuming and filtration
  • Detailed cleaning
  • Temperature and humidity control

These engineering controls affect many aspects of air duct cleaning. Some of which you may not normally think of. They include:

  • Equipment maintenance: All your equipment shall be in good working order.
    • Before the project: clean and inspect your equipment to ensure that you don’t introduce any contaminates.
    • During the project: maintain/service equipment as needed to limit possible cross-contamination.
    • Filter maintenance during the project: If you need to open your vacuum collection system on-site to service/change filters do so in a containment area or outside the building.
  • Equipment transportation/relocation: all equipment shall be clean and sealed before relocating or removing from building.
    • On-site equipment verification; it is recommended that on-site maintenance verification be performed on vacuum collection equipment prior to its use.
  • Fuel powered equipment: shall be positioned to prevent emissions from entering the building.
  • Vacuum equipment exhausting indoors: shall utilize HEPA filtration with 99.97% collection efficiency to 0.3 micron particle size.
  • Negative pressure requirements: continuous negative pressure shall be maintained in the portion of the HVAC system being cleaned in relation to the surrounding indoor space.
  • Handling of contaminated materials: all contaminated materials shall be properly contained prior to removal from building.
  • Ambient air cleaning: it is recommended that ambient air cleaning using HEPA filtered air scrubbers be used during and after HVAC cleaning and restoration to provide at least 4 air changes per hour.
  • Control of product emissions: follow manufactures application recommendations, including exhaust ventilation as required when using cleaning agents and chemicals.
  • Negative pressure failure: it is recommended that back-up equipment be on-site with a dedicated power supply to prevent negative pressure failure due to equipment malfunction or electrical power interruption.

According to NADCA’s ACR 2013 Cleaning Standard there are four levels of containment you can use to prevent cross-contamination.

  • Level 1: minimal level, used on all projects
    • Negative pressure
    • Protective coverings
    • Cleaning equipment & tools
    • Cross-contamination control    
  • Level 2: include Level 1, plus temporary barriers
    • Temporary containment barriers
    • Containment of area floor
    • Validate negative pressurization
    • Ambient air cleaning
    • Dismantling
  • Level 3: includes Level 1 & 2, plus a single decontamination chamber
    • Decontamination facility
    • Monitoring requirements
  • Level 4: includes Level 1, 2 & 3, plus two decontamination chambers
    • Decontamination facility
    • Monitoring requirements

You should use appropriate engineering controls are on every HVAC cleaning and restoration project. Protecting workers, building occupants and preventing cross contamination should be your top priority.  

Additional information on engineering controls can be found in Section 3 of NADC’s ACR 2013 Cleaning Standard. If you have any questions about this article please contact Peter Haugen, ASCS, CVI at 855-Vac-Systems or phaugen@vacsysint.com.


Tags: air duct cleaning, air duct cleaning engineering controls, engineering controls