Understanding laboratory ventilation codes

Become familiar with the project parameters and governing codes and standards to provide good HVAC design, proper airflow, and correct pressure relationships for your project and client.


Clinical laboratories are often on-site and associated with hospitals, but many times these facilities are independent and located away from the source of patient care and treatment. Regardless of the lab location, published rules and regulations apply to the design, layout, finishes, equipment, ventilation, and operation of the facility. While this article identifies many of the latest code and standard editions, it is always prudent to check with the local and state authorities having jurisdiction (AHJ) to confirm the latest adopted version.

Clinical labs have multiple functions and generally include such uses as general chemistry, hematology, urinalysis, pathology-histology, cytology, frozen section, chemical and specimen storage, and refrigerated blood storage. Some laboratories also contain and process hazardous and/or flammable materials or radioactive materials, and they require specific hood types and storage containers with limits on quantities of material. NFPA 45 (2011), Standard on Fire Protection for Laboratories Using Chemicals, is the basic NFPA standard for laboratories. It covers the construction, ventilation systems, and related fire protection for all laboratories in all facilities. However, Chapter 11 of NFPA 99 (2005 Edition), Standard for Healthcare Facilities, has more stringent requirements for laboratories located in healthcare facilities. The primary focus of each of these standards is to establish criteria to minimize the hazards of fire and explosions in laboratories. The standards are not intended to cover hazards resulting from the misuse of chemicals, radioactive materials, or biological materials that will not result in fires or explosions. However, many of the requirements that protect against fire or explosions, such as those for hood exhaust systems, also serve to protect individuals from exposure to nonfire health hazards of the material.

The 2009 edition of NFPA 101, Life Safety Code, in Chapters 18 and 19 for new and existing healthcare occupancies, establishes minimum construction criteria, egress requirements, and hazardous area descriptions with fire protection/separation requirements for laboratories. Ventilation requirements for laboratories within healthcare facilities are deferred to NFPA 99, which then references NFPA 45, which serves as the basic standard for laboratories.

Sound circular? Not really. These codes and standards are written to complement each other, not necessarily repeat each other, and therefore minimize the potential for conflict. However, as NFPA 99 points out, certain requirements are more stringent depending on the occupancy classification of the building or portion of the building.

The 2011 edition of NFPA 45 also identifies that laboratories located in healthcare facilities previously covered by NFPA 99 were added to NFPA 45. This current version also modifies Chapters 4, 5, 9, 10, and 11 of the previous edition that deals with the design, construction, and operational requirements for laboratories. It also added height restrictions for Class A and B units and clarified hazardous materials in storage for use in laboratory work areas that could present an explosion hazard. Also, a revised and rewritten edition of NFPA 99 will be released in 2012.

The 2006 AIA Guidelines for Design and Construction of Health Care Facilities, as well as the newest 2010 Facility Guidelines Institute (FGI) Guidelines for Design and Construction of Health Care Facilities (which includes ASHRAE/ASHE Standard 170), list minimum air change rates for laboratories at 6 to 10 ACH, depending on the space function. However, some local and state codes may require higher minimum air change rates than the aforementioned guidelines. The most stringent requirements based on the comparison of applicable codes should be utilized. Pressure relationships are generally negative (air movement in) with respect to adjacent spaces. Supply air distribution within lab spaces and rooms should be arranged and devices chosen to avoid air currents that would adversely affect the performance of chemical fume hoods. Many codes such as ASHRAE 170 in the 2010 FGI Guidelines require proper air filtration and generally require one filter bed, at MERV 13 upstream, and recommend an additional MERV 7 filter for protection of the MERV 13 filter for all air supplied to the laboratory. There is nothing in any of the codes or good engineering practice that prevents the designer from using two filter beds, one upstream and one downstream of the fan for all air supplied to these spaces.

Both NFPA 99 and NFPA 45 cover the quantities of flammable and combustible material allowed to be stored in a lab. The containers in which they are stored are covered by NFPA 30, Flammable and Combustible Liquids Code, 2003 edition.

Chapter 8 of NFPA 45 prescribes requirements for laboratory ventilating systems and hood requirements. The chapter applies to supply air systems, laboratory exhaust systems, lab hood exhaust, and chemical fume hood exhaust. According to the standard, all laboratory ventilation systems should be designed to ensure that fire hazards and risks are minimized. Under normal operating conditions, all lab hoods in which chemicals are present should be continuously ventilated. Each hood has its own exhaust requirements that relate to proper open sash face velocity to protect lab personnel. The code requires proper hood exhaust ducting, fan selection, and makeup air delivery. In all cases, the fan must be located at the discharge of the duct system. The 2006 and 2009 International Mechanical Code, Section 510, governs the design and construction of duct systems for hazardous exhaust and determines where such systems are required. These hazardous exhaust systems should be independent of other types of exhaust systems and should not share common shafts with other duct systems, except where such systems are exhausting similar compatible materials and originate in the same fire compartment. HVAC and duct systems handling radioactive materials also have specific requirements and are further governed by NFPA 801, Fire Protection for Facilities for Handling Radioactive Materials.

Supply air and exhaust air balancing within lab spaces is extremely critical, because these air systems must prevent a pressure differential that would impede egress or ingress when either air system fails during an emergency scenario. Air systems must be designed to prevent the recirculation of flammable or combustible or chemical fumes within the lab space. The location of fresh air intakes must be chosen to prevent the entrainment of chemical fumes or vapors from the lab exhaust discharge or from other sources in adjacent buildings. As for HVAC controls, system equipment redundancy, reliability and electrical power requirements to achieve proper space temperatures, air change rates, and pressure relationships, these factors are left to the HVAC design engineer to properly design, specify, and assist in commissioning to make the systems functional and have repeatable results on an ongoing basis.

The Centers for Medicare and Medicaid Services (CMS) regulates all laboratory testing (except research) performed on humans in the United States through the Clinical Laboratory Improvement Amendments (CLIA). The objective of the CLIA program is to ensure quality laboratory testing. This relates directly to the fact that all clinical laboratories must be properly certified to receive Medicare or Medicaid payment; however, the CLIA has no direct CMS program responsibilities.

Another agency that has requirements that accredit clinical laboratories is the College of American Pathologists (CAP). CAP uses the CLIA-based Laboratory Accreditation program and is recognized by both CMS and The Joint Commission (TJC). The goal of the CAP accreditation program is to improve patient safety by advancing the quality of pathology and laboratory services through educating laboratory designers and staff, setting standards, and ensuring laboratories meet or exceed regulatory requirements. While a majority of the CAP inspection and checklists relate to the formal and actual lab process and procedures, a portion of the checklists relate to the physical space regulatory requirements that require proper temperature, air change rates, air direction, and flow that improve staff safety and work quality in the laboratory. The CAP program generally satisfies TJC requirements and can be used to meet many state certification requirements. Becoming familiar with the functional and operational aspects of laboratories is a key to providing proper air delivery and pickup that will not interfere with hood operation, keep slides from drying out, and capture potentially harmful fumes to protect lab staff.

The CDC/NIH publication, “Biosafety in Microbiological and Biomedical Laboratories,” also serves as an advisory document recommending best design practices in biomedical and clinical laboratories from a biosafety perspective, especially for higher biosafety level contaminants, such as Biosafety Level 3 (BSL-3) and above.

Become familiar with the project parameters and governing codes and standards to provide good HVAC design, proper airflow, and correct pressure relationships for your project and client.

Banse has more than 35 years of experience in the consulting engineering field with the past 30 years in healthcare design and engineering. He is a member of Consulting-Specifying Engineer's Editorial Advisory Board.

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