What Are Air Duct Cleaning Engineering Controls?

Engineering controls are methods used to ensure worker and building occupant safety/health and to prevent cross-contamination during HVAC system 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: Before the project: clean and inspect equipment to ensure that no contaminates are introduced.
During the project: maintain/service equipment as needed to limit possible cross-contamination.
Filter maintenance during the project: if vacuum collection system on-site need to be opened 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 manufacture’s 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.

There are four levels of containment that 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

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

Appropriate engineering controls should be used on every HVAC cleaning and restoration project. Protecting workers, building occupants and preventing cross contamination should be a top priority.