Solution Summary: Pre-task planning for duct maintenance/demo

Existing ductwork may contain chemical, biological, or radiological residue that is hazardous upon proximity, contact, inhalation or ingestion. These materials may not be easily characterized and may not be visible.

The contractor should require the owner to fully determine the past use of each duct system that is to be maintained or demolished, to characterize the potential hazards, and to decontaminated the ducts. To the extent that the owner cannot or does not perform these functions, sheet metal workers and others performing demolition or maintenance should follow a safety plan prepared by a qualified person that includes the specification of appropriate PPE, methods for demolition, the availability of emergency and routine decontamination facilities and a reliable emergency communication system.

Description:

Steps in the maintenance, cleaning or demolition of existing ductwork, to be performed in sequence:

Identify and contact the operational owner of the ducting
Determine with the operational owner or their authorized representative the current and past function of the ducting and whether it needs to be treated as hazardous or non-hazardous. If the line has carried or may contain VOCs, toxic or corrosives material, radioactive material or harmful biological agents it should be treated as hazardous until completely decontaminated. A duct may be connected to more than one source and may contain more than one type of hazard. The ducting should be labeled to identify what chemicals the ducting was exposed to, the status of decontamination and any residual hazards to future handlers.
Coordinate with the appropriate persons representing site environmental, health and safety to ensure decontamination of the ducting prior to demolition or maintenance and proper disposal of demolished components.
Notify all appropriate persons prior to beginning and upon completing work.
Identify and shut down anything that can pressurize the duct or add gases. Purge to atmospheric pressure.
Seal all ports and opening.
Confirm that all surfaces exposed to corrosives test to a P^H between 5 and 9
Develop and define dust and liquid containment for the job
Determine the type and level of PPE to be used for each stage of the job. Ensure adequate eye, skin and respiratory protection
Identify a decontamination area for doffing PPE.
If there is any possibility of contact with toxic or corrosive liquids a safety shower and eye wash station must be identified or established within ten seconds unobstructed travel (about 50 feet) from each potential site of exposure. Portable stations may be moved as the work progresses
Identify and control all other hazards
Barricade area and post warning signs
Don specified PPE
Begin demolition at the highest point on the exhaust duct and work toward the lowest end. Dismantle with care, sealing all extremities of components as soon as they are removed.
Do not use a torch to cut any potentially contaminated section. Use mechanical cutting or separate at connection points
Properly dispose of demolished sections.
Decontaminate workers and tools. Correctly dispose of contaminated protective clothing

Duct Inspection and Decontamination

Exterior inspection and decontamination

Potentially contaminated exterior surfaces should be swipe sampled and P^H measured. If contaminated, the exterior of the duct should be cleaned first. Appropriate PPE must be worn during this operation.

Interior duct inspection and decontamination

To provide for visual inspect, drill a 9/16th inch or slightly larger hole in the top 1/3 of the duct starting at the highest horizontal section and then at each 8 foot interval and at each horizontal change in direction. Use a borescope to perform a visual inspection of internal duct surfaces to locate any freestanding liquid or solids buildup. If < 1 pint of liquid is located, cut a sufficiently large access hole in the upper 1/3 of the duct and use absorbent pillows or other absorbent material to absorb all liquids in the ducts, leaving the material in the duct. If> 1 pint of liquid is present stop work and develop a work plan. If solid material is located, build a visquine containment around the area to minimize dust. Accumulated dust may be removed using a vacuum connected to a HEPA filter.

Rigid and flexible borescopes are available from Gradient Lens Corporation, Fiberscope , Lenox Instrument, and Olympus. A steerable, articulating video borescope with a working length of 100 feet is available from GE.

Risks Addressed:

Exposure to toxic, corrosive, biologically active or radiological dust, liquids or solids in or on ventilation ductwork.

How Risks are Reduced:

Pre-job coordination, planning, hazard recognition and decontamination. Use of appropriate PPE when ducts are not completely decontaminated.

Industry best practice

Effects on Productivity:

Hazard recognition and preplanning are essential elements of maintenance and demolition work. Required time and resoureces should be included in job bidding. Improper planning, hazard recognition or decontamination may lead to worker injuries or illness and environmental contamination.

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