Two primary factors make Standard 188 the mother of all Legionella documents issued in the United States up to now.

First, it will be a standard, not just a guideline. It is slated to become an ANSI standard as well as an ASHRAE standard. In terms of legal risk, breaching a standard is more serious than choosing not to follow a guideline.

Second, and probably more important, is consensus. Although several Legionella guidelines have been issued in the United States, including ASHRAE Guideline 12-2000, none has received broad support among government agencies, Legionella experts, and industry groups as has the pending ASHRAE Standard 188. 

The standard will likely impact insurance coverage, lawsuits related to Legionnaires' disease, and plumbing codes. It may even become law in some states.

ASHRAE Standard 188, "Prevention of Legionellosis Associated with Building Water Systems," will require a Legionella HACCP water plan, not only for buildings like hospitals and nursing homes that have occupants at higher risk of contracting Legionnaires' disease, but also for office buildings, apartment buildings, hotels and other buildings that have ten or more stories, centralized water heaters, or an incoming water supply with a chlorine concentration of less than 0.5 parts per million. The standard will also require HACCP principles in the maintenance of cooling towers, whirlpool spas, ornamental fountains, misters, air washers, and humidifiers.

Responsibility for complying with the new ASHRAE standard will fall primarily on building owners but will also affect architects, engineers, contractors, and water treatment companies.

The HACCP (Hazard Analysis and Critical Control Point) process involves seven principles:

1.  Conduct a hazard analysis. 2.  Identify critical control points. 3.  Establish critical limits. 4.  Monitor performance. 5.  Take corrective action. 6.  Verify and validate. 7.  Document the plan.

HACCP has been used for years in the food industry and since 2007 has been advocated by the World Health Organization in managing building water systems for the control of Legionella bacteria (WHO. 2007. Legionella and the prevention of legionellosis. Geneva: World Health Organization).

It is a written plan for using the HACCP approach in managing building water systems for the prevention of legionellosis.

Developing and implementing a Legionella HACCP water plan per ASHRAE Standard 188P boils down to eight steps:

1. Form a team to oversee the plan.

2. Perform a water systems survey and construct flow diagrams identifying all the building water system points (e.g., points of entry) and processing steps (e.g., water heaters). ASHRAE Standard 188P requires that the Legionella HACCP water plan include at least two flow diagrams—one for potable (domestic) and nonpotable (utility) systems.

3. In hazard analysis summary tables, identify the water systems having the potential of harboring and transmitting Legionella bacteria.

4. Determine points (critical control points) where control measures can and should be applied.

5. Establish control measures for each critical control point with specifications for performance limits, monitoring to see if the control measure is being performed according within the performance limits, frequency of monitoring, and corrective action if performance is subpar. Control measures should be evidence based, up to date with scientific findings and technology, reasonable in cost, as simple as practical, and clear to all the people involved in implementing them.

6. Document the control measures outlined in your plan.

7. Verify that the HACCP plan is being implemented.

8. Validate the effectiveness of the plan in preventing Legionnaires' disease.

As an example, consider a hotel property with four 15-story towers, two swimming pools, four hot tubs, and one cooling water system (four cooling tower cells and four chillers), and three water features, as well as fire protection, heating hot water, and irrigation systems. The owner would need only one Legionella HACCP water plan assuming all four buildings are on the same campus, served by the same water supply, and managed by the same personnel. The points (e.g., points of building entry) and processing steps (e.g., domestic water heaters) for the water systems would need to be listed in hazard analysis summaries and illustrated in flow diagrams. For those determined to present a significant potential for Legionella growth and transmission, control measures would be established at critical control points. Specific performance limits would be established for each control measure, along with a monitoring method and frequency for checking the performance, and corrective action to take if the performance limit is not met. The measures would need to be documented and the documentation checked periodically by the person responsible for verifying implementation.  Finally, the effectiveness of the plan in preventing legionellosis would have to be validated.