The National Air Duct Cleaners Association (NADCA) has released the much-anticipated public review draft of the organization's new Standard for Assessment, Cleaning and Restoration of HVAC Systems for Hygiene, otherwise known as ACR-2000. The document is available free of charge via the NADCA website (www.nadca.com) during a 60-day comment period that began at the beginning of this month.

This article provides an overview of the standard's primary sections, including commentary regarding new material added since the 1992 publication of ACR-2000's predecessor, NADCA Standard 01, Mechanical Cleaning of Non-Porous Air Conveyance System Components.

Standard 01-1992 limited its scope to fundamental HVAC system cleaning project requirements and methods to evaluate cleaning effectiveness. ACR-2000 attempts to establish far more detailed project requirements as well as strict criteria for a whole new range of elements related to system maintenance and construction. Like the original NADCA standard, ACR-2000 defines methods and procedures to measure system cleanliness. The new standard also includes a unique system that integrates building classification, debris identification and applicable engineering controls to produce project specifications and criteria.

A Broad Scope
According to Section 1.1, Scope, ACR-2000 establishes requirements for cleaning contractors and their clients, as well as for IAQ professionals who investigate HVAC system cleanliness and condition. These requirements cover system assessment, cleaning methods and equipment for both general hygiene and HVAC system performance.

Going further, the requirements within ACR-2000 are categorized and systematized to "address occupancy type, building use, contaminant type, worker and occupant health and safety, environmental engineering controls, project monitoring, remediation; and environmental considerations for removal and installation of HVAC components." That's a tremendous scope, and critics of the standard may argue that NADCA has stepped outside its members' domain in certain areas.

While Section 1 is titled "General," subpart 4 goes beyond general and probably could stand as a section unto itself. Titled, "When to Remediate," 1.4 provides information consumers and contractors have requested for years - a guide to determining when HVAC system cleaning is really needed. According to ACR-2000, if an assessment reveals any of four adverse conditions, remediation is required. For example, evidence of "significant quantity of particulate or debris" within a system "which may adversely affect the indoor environment or HVAC system performance" mandates cleaning. Unfortunately, however, the standard fails to qualify key terms like "significant quantity" and "adversely affect."

When particulate is discharged from the HVAC system into occupied spaces, ACR-2000 mandates cleaning. The standard includes an appendix that describes a procedure called "Aggressive Particle Profiling" that compares particulate levels in the return space (before filtration) with levels distributed by supply ducts. This procedure enables the standard's user to determine of the HVAC system is releasing contaminants into occupied spaces. The procedures specified in the appendix are difficult to follow, however, and should be rewritten and explained with greater clarity.

Other times system remediation is required include when system performance is compromised due to debris blockages within mechanical components, when contamination is left behind after system installation or retrofit, and as part of a proactive hygiene maintenance program.

Assessment
Section 2 of ACR-2000 breaks important ground. It describes how procedures common to HVAC system cleaning may negatively affect the indoor environment, and it requires a complete assessment of how cleaning processes will be managed to prevent any additional contamination of occupied spaces. A more detailed discussion of specific procedures that might expose occupants to contaminants would greatly enhance the engineering controls to contain debris during cleaning that are defined in section 5 of the standard.

"HVAC Hygiene Assessment" is the third section of the standard. It describes the areas of a system that must be evaluated in order to determine the need for cleaning. More importantly to the overall construction of the standard, however, is a unique set of building classifications and associated assessment criteria contained in this section. Buildings are classified as follows: Class 1 - Industrial; Class 2 - Residential; Class 3 - Light Commercial; Class 4 - Commercial; Class 5 - Health Care; Class 6 - Marine; and Class 7 - Special Use Areas. The first part of Section 3 addresses cleanliness assessment criteria common to all classes of buildings, such as HVAC component condition, contamination levels and system performance abnormalities. This is followed by subparts for each building classification that contain assessment criteria that may be unique to a particular class.

While the assessment criteria make sense overall, some appear unrealistic. For example, a "commercial" building hygiene assessment must include particulate profile testing using the Aggressive Particle Profile procedure described in Appendix C. Also required is air testing and balancing "to determine if deposits and/or contaminants are contributing to a reduction in system performance." Given the myriad of factors beyond cleanliness that may affect system performance, not to mention cost involved, the practicality of testing and balancing as part of a hygiene assessment is questionable.

Section 4, HVAC Hygiene Maintenance, defines minimum inspection frequencies for the classes of buildings defined in Section 3. Classes 1 to 4 require annual hygiene assessments of air handling units and representative sections of supply and return ductwork. In more sensitive environments, frequency increases.

Specification Development And Project Planning
A key component of ACR-2000 is Section 5. Here NADCA attempts to provide a standard for the development of project specifications and requirements using a series of tables that build upon one another. In the first table the building classification is established. Within the second table, the project type - A, B, or C - is determined based on whether there is debris or particulate contamination, and microbial contamination, within the HVAC system. With the project type known (although many projects could fall into types B or C without a clear distinction why), a third table maps out the degree to which 13 different engineering controls must be employed.

As an example, in a commercial building with dust and mold in the HVAC system (type B or possibly C) ambient air cleaning is required during and after cleaning, "to provide ambient airborne particle reduction." If the system were only to contain dust and no mold, then it would be classified type A and ambient air cleaning would be recommended but not required. When carefully studied, the overall system of tables does make sense. It took this reviewer about an hour to figure out how the system works. The failure to clearly delineate when a project is type B versus C, however, is a weakness that must be corrected. The current ambiguity leaves too much room for incongruity between projects of a similar size and scope.

Ultimately, if NADCA expects the marketplace to adopt its system for specification development and project planning, the association will need to conduct workshops for facility managers and engineers to teach them how to apply the standard to their buildings. For residential applications, the system is impractical from a consumer's point of view, since few homeowners would take the time or have the wherewithal to figure it out.

Supplemented by NADCA's existing safety manuals for contractors, Section 6 of ACR-2000 covers health and safety issues for workers adequately. Section 7 repeats the key provisions of NADCA Standard 05, Requirements for the Installation of Service Openings in HVAC Systems, along with a few improvements to the 1997 access door standard.

Cleaning
Section 8, Mechanical Cleaning of HVAC Systems, reconfirms some of the principles that have guided NADCA since its inception, such as the use of Source Removal cleaning techniques and prohibitions against the use of encapsulants to trap debris in place. The necessity to include some method of agitating or dislodging debris is set forth; however, specific methods are not listed. Requirements for use of tools like manual brushes, compressed airwhips, cleaning robots and mechanical brushes could help prevent system damage from improper use but are not provided.

Subpart 8.2 covers Remote Vacuum Collection - the use of a large vacuum to create sufficient air movement within a section of an HVAC system to entrain and remove particles of debris. A table is provided that defines required air movement velocity to collect a wide variety of dust types.

How Clean Is Clean?
Answering the question, How Clean is Clean?, was a primary goal when NADCA wrote Standard 01 in 1992. ACR-2000 also covers this territory, although the precise details have yet to be released for one cleanliness verification method and the draft is therefore incomplete in this section.

Three levels of cleanliness verification are set apart. The first is visual inspection. If visual inspection disputes that acceptable cleanliness levels have been achieved, the next level come into play - the NADCA Contact Vacuum Test. The test defined in the standard is a hybrid of the verification method contained in Standard 01-1992. Improvements to the method developed three years ago during joint NADCA-EPA research are included in the new standard.

The third level of cleanliness verification has yet to be published. It is called the "NADCA Quantitative Vacuum Test" and within the draft version of ACR-2000 readers are informed that this test method is under development.
According to the standard, cleanliness verification must be performed before the system or component is placed into operation. While this make sense from a contractor perspective - external factors might contaminate a just-cleaned system - in reality it's not a very practical requirement to follow. If followed to the letter, a consumer would be required to have an inspector on-site as each component was completed and placed back on line. While some commercial consumers may be willing to take such an approach, many would find it cost prohibitive and restrictive. The standard requires the client to "assign a representative to act as an assurance manager for verifying the HVAC component post cleaning." It goes onto specify that if no such manager is assigned, "the contractor shall perform post-cleaning assessments." This is likewise not the best solution - the old fox watching the hen-house scenario.

Section 10 of the standard addresses Remediation of Biological Contamination. A significant portion addresses porous materials (e.g., fiberglass), and recommends removal and replacement when possible in most instances. Other requirements call for the implementation of management plans to locate and correct the system deficiencies that allowed moisture and debris to accumulate and foster microbial growth.

Restoration
The restoration section of ACR-2000, Section 11, primarily covers restoration of damaged fiberglass liner. First an assessment of HVAC system component condition is specified. Acoustical lining damaged by fire, smoke, flood or water-damage must be evaluated for resurfacing or replacement. Some criteria are also defined for the use of encapsulating and coating products.

While adequate in the area of fiberglass assessment and refurbishment, the restoration section lacks detail regarding fire and water restoration decontamination procedures. For instance, NADCA should consider adopting some of the provisions from Institute of Inspection Cleaning and Restoration Certification (IICRC) Standard S500, Water Damage Restoration. An understanding of the different categories of water in water-damage situations should be incorporated into the assessment of the HVAC system when water damage is the primary contamination source. Clean water decontamination procedures would obviously require less stringent controls and methods than decontamination after damage from a sewer backup.

Extending Their Domain
In Section 12, Maintaining the Indoor Environment During HVAC Remediation and Commissioning, ACR-2000 addresses subjects that go beyond the scope of what people might think the NADCA standard would include. It calls for an environmental impact study before activities such as HVAC system repair, retrofit, installation and commissioning. In essence, the section attempts to establish engineering controls to protect the indoor environment from contamination by HVAC system pollutants during all HVAC repair and engineering activities. The goal is admirable, but a separate environmental control standard for these activities could easily stand on its own. And it would seem logical for the creation of such a standard to be initiated by professionals in the fields most affected: HVAC contracting, engineering and test and balance.

The final section of the standard is titled Project Monitoring and it details steps to be taken to monitor and evaluate the effectiveness of engineering controls implemented to protect the indoor environment.

Confusing Parts
While commendable for its ambitious scope, ACR-2000 is difficult to follow in a few key areas. This especially the case in Section 5, where a series of charts are provided to assist in classifying buildings, project types and appropriate engineering controls. The charts are helpful, but a more detailed explanation of how to use them, as well their limitations, is needed within the text of the section.

Perhaps as a result of their efforts to get a draft standard on the street before NADCA's annual convention next month in Phoenix, errors in section numbering, spelling mistakes and other typos make certain sections document particularly confusing. An incorrectly numbered chart that defines environmental engineering controls for different types of facilities and contamination levels left this reviewer frustrated and perplexed until the error was recognized.

When NADCA Standard 01-1992 was drafted, it went out for a 90-day review and the association received a lot of feedback from industry experts and trade groups. Key professionals from groups such as ASHRAE Standard 62 subcommittee, ARI technical staff, NAIMA and others gave positive feedback enabling NADCA to produce a standard that has been well respected for almost a decade. With the comment period reduced by 30 days and the scope of the standard increased dramatically, one hopes that such professionals will still find the time and energy to give meaningful comments. For while ACR-2000 is certainly in need of revisions, at its core it contains some valuable, innovative information and requirements that could help to improve the HVAC system cleaning industry and protect its consumers.