Designing laboratory veanotiltin syestms

1 BY J. PATRICK BANSE, PE, and CHRIS ST. CYR, Smith Seckman Reid Inc., Houston36 Consulting-Specifying Engineer JANUARY/FEBRUARY 2014 ventilation of laboratory set-tings is required to promote and maintain laboratory safety and pro-tection to life and property. Items such as fume containment, worker safety, proper cleanliness through pressure relation-ships, filtration, air changes per hour (ACH), point of fume capture, tempera-ture, and relative humidity requirements are elements necessary to design the ven-tilation system depending on the labora-tory type.

2 Codes identify ventilation mea-sures to provide minimum requirements for the protection of life and property through prevention and control of fumes and containment of hazardous fumes and contami-nants for worker are four general types of laboratories noted in the ASHRAE Handbook HVAC Applications:1. Biological: Contains bio-logically active materials and includes areas such as biochem-istry, cell biology, immunology, pharmacology, microbiology, and related fields. Clinical lab-oratories fall into this Chemical laboratories that support both organic and inor-ganic synthesis and analytical Animal labs that include areas for the observation, manipulation, and pharmaco-logical observation of laboratory animals and also include animal holding Physical laboratories are spaces associated with physics and include lasers, optics, high- and low-temperature materials, and analytical laboratories commonly have chemical fume hoods and Class I and Class II bio-safety cabinets.

3 Chemi-cal labs generally have a number of fume article will provide information on hood types and ventilation criteria primar-ily on the first three types of labs, with discussion on contaminant containment, airflow practices, comfort conditioning, and the codes that govern the lab ventila-tion codes and standardsThe 2011 edition of NFPA 45: Standard on Fire Protection for Laboratories Using Chemicals applies to laboratory buildings, units, and work areas in which defined chemicals are handled or stored. Chap-ter 8, laboratory Ventilating System and Hood Requirements, defines criteria and considerations for exhaust air and supply air systems including requirements for fume hood - laboratory Ventilation describes required and recom-mended practices for the design and opera-tion of lab ventilation systems for control of exposure to airborne contaminants.

4 It does not apply to animal facilities, laminar Figure 1: Standard constant volume fume hood shows a typical airflow pattern. All graphics cour-tesy: Smith Seckman ReidFigure 1: Standard constant volume fume hood FloorCeilingExhaust ductFumehoodAir flowOpen sash Fume hood bypass constantvolume (sash open)Proper ventilation in labs is required to promote and maintain safetyand protection to life and laboratory ventilation systemsLearningobjectives Understand the codes and standards that guide labora-tory ventilation design. Learn how to design labora-tory ventilation systems to meet system requirements.

5 Understand key equipment Consulting-Specifying Engineer JANUARY/FEBRUARY 2014flow hoods, or bio-safety cabinets. Chap-ter 5 of this standard discusses laboratory ventilation system designs. In the 2011 ASHRAE Handbook HVAC Applications, Chapter 16 pro-vides detailed descriptions of laboratory airflow, fume hood types, hazard assess-ments, exhaust systems, and applications to various lab types. NFPA 99: Health Care Facilities Code, 2012 edition, has deleted the previously included chapter pertaining to laborato-ries and has added a new Chapter 4, which establishes four Categories of Risk.

6 Also included is Chapter 9 outlining HVAC requirements for health care facilities. Ref-erences are made in this chapter to NFPA 45 and ASHRAE Standards , 90A, and 170. This code will pertain primarily to clinical labs and related spaces whether within a hospital or separate 2010 edition of FGI Guidelines for Design and Construction of Health-care Facilities incorporates ASHRAE 170-2008 (with addenda): Ventilation of Health Care Facilities, which has spe-cific requirements for laboratory ventila-tion including pressure relationships, air change rates, and temperature and relative humidity requirements.

7 ASHRAE Standard : Ventilation for Acceptable Indoor Air Quality identifies minimum ventilation rates in the breathing zone (Table 6-1) and minimum exhaust rates (Table 6-4) for laboratories and other spaces. (Standard was released in Novem-ber 2013.) The International Building Code (IBC) in the occupancy chapter 304 defines testing and research laboratories as a Busi-ness Group B occupancy. The International Mechanical Code (IMC) in Table identifies minimum ventilation rates for science laboratories, and sec-tion 510 explains the require-ments for laboratory exhaust systems.

8 There are other standards as well, such as OSHA 29 CFR : Occupational exposure to hazardous chemicals in laboratories and 21 CFR 58: Good laboratory Practice Regulations, which while giving guid-ance, do not specifically require or specify ventilation rates or practices. The more recent editions of several codes and standards have less focus on minimum or required air change rates and more focus on proper capture of fumes and contaminants, protection of workers, proper hood design and sash face velocity, supply air distribution, and pressure relationships.

9 As with any project design, it is appropri-ate to determine which codes and standards are officially adopted by the authority hav-ing jurisdiction (AHJ) so that the correct and more stringent requirements can be incorpo-rated into the hood typesSome common types of fume hoods used in clinical and chemical labs include standard fume hoods (constant volume exhaust airflow with variable face velocity) shown in Figure 1; bypass fume hood (constant volume exhaust airflow) shown in Figure 2; variable volume fume hood (constant face velocity); and auxiliary air fume hood (constant volume exhaust airflow with 50% to 70% makeup air directly to hood).

10 Additionally, there are biological safety cabinets used in clinical lab set-tings that include Class I, which is simi-lar to a chemical fume hood (see Figure 3); and a Class II A1 bio-safety cabinet that includes high-efficiency particulate absorption (HEPA) supply filters and HEPA exhaust filters that allow air to be re-circulated to the lab or exhausted directly outside (see Figure 4). A Class II B1 bio-safety cabinet is simi-lar; however, all air is removed through a HEPA filter and exhausted directly outside. A Class III bio-safety cabinet is completely enclosed and the work is done through gloves attached to the cabinet.