New Construction: General Requirements for Duct Cleanliness

During new construction projects, special care needs to be taken to ensure HVAC ductwork remains clean and free of contaminants. If new ductwork gets contaminated with dirt, mold, sawdust, volatile chemicals, or other remnants of the construction process, your building’s indoor air will be compromised when your HVAC system is activated.

These sorts of contaminants can adversely affect the health and comfort of employees and customers. To maintain duct cleanliness on the building site and keep new ductwork clean and free of particulates and other material, construction professionals should apply the following general requirements.

Duct Cleanliness Levels

The Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA) lists three distinct duct cleanliness levels: basic, intermediate and advanced. Each level carries its own criteria for duct conditions. More advanced levels also incorporate the conditions and criteria set out in the lower level. Basic level: When leaving the manufacturer, ductwork at the basic cleanliness level can have:

• Internal or external self-adhesive identification labels.
• Exposed mastic (a specialized duct sealant).
• A light coating of oil.
• Light zinc oxide surface coating.
• Internal insulation and fasteners.
• Discoloration from plasma cutting procedures.

The presence of bolts, rivets, screws, or other minor protrusions in the internal air pathway. Ductwork at the basic level must be protected from damage during shipping, but does not have to be covered. Sections should be inspected for contamination before installation. Debris and other materials in the ductwork should be removed.

Intermediate level: This level of duct cleanliness requires ductwork storage areas to be clean and dry, with minimal exposure to dust and other contaminants. Internal surfaces should be wiped down to remove dust and contaminants before installation, while open sections of ductwork should be covered to protect ducts during breaks in the construction process.

Advanced level: Advanced level duct cleanliness requires that self-adhesive identification labels be attached only on external surfaces. Ductwork sections should be covered, wrapped, or capped during transportation and storage. Storage environments should be clean and dry, and sealed ends should be inspected and resealed if damage occurs during storage. Construction requirements may set out additional or different criteria for duct cleanliness and the handling of duct cleaning and installation. If local documents are more stringent than SMACNA standards, they should be used as the duct standard for any particular project.

Duct Design and Access

HVAC ductwork design must ensure the transportation of sufficient amounts of heated and cooled air to keep indoor spaces comfortable. In this context, indoor air quality is becoming more of an issue in modern construction. Duct cleanliness is a major component of maintaining an acceptable level of indoor air quality. For this reason, newly installed ducts should have an increased number of duct access panels in addition to regular access panels.

More access panels increases the ability for maintenance and HVAC personnel to inspect ducts for contaminants and clean them when necessary. Additional access panels should be installed at major transition and junction points, at points along lengthy sections of straight ductwork and at the top and bottom of vertical ducts that penetrate multiple floors.

Job Site Conditions

When ductwork is being stored, moved, handled, or installed on the job site, care should be taken to ensure the duct sections are not contaminated with particulates and other materials. Protective covers should be left in place until the duct sections are actually being installed. By practicing good overall cleanliness on the job site, the likelihood of contaminating ductwork is significantly reduced.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection, and Alarm Systems in Mechanical, Commercial, and Residential settings. For more information on duct cleanliness and techniques contractors and engineers can use to keep new ductwork clean, and to view projects we’ve worked on, visit our website!