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Laboratory Safety Manual

Reviewed May 2012

Chapter 7: Administrative Concerns
Section 7.3 - Facility Design

F.   Ventilation, Indoor Air Quality, Heating, and Cooling

While specific sources of laboratory related emissions are generally controlled, with fume hoods and local exhaust ventilation, general room and building ventilation has a considerable effect on the air quality in the laboratory and its associated offices. A facility ventilation system which provides even circulation and sufficient indoor/outdoor air exchange serves the comfort and safety of the occupants by reducing indoor air contaminant levels. Variable volume air systems should be avoided so that air contaminant levels may be precisely controlled.

The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Standard 62 "Ventilation for Acceptable Indoor Air Quality" addresses ventilation rates of buildings by offering recommendations for maximum indoor air contaminant concentrations as well as volumes of fresh air expected to provide air test results lower than those concentrations.

In design of the ventilation system, air intakes and exhausts should be located so as to avoid re-entrainment of contaminated air. Also, additional general ventilation may be required for stockroom and storerooms in the facility.

Closely related to the ventilation requirements is the need for proper heating and cooling of room air in the laboratory. ASHRAE Standard 55 "Thermal Environmental Conditions for Human Occupancy" addresses this subject.

Separate systems may be required for the specific requirements of certain types of analytical equipment and computer operations.

G.  Ventilation Hoods

  1. Laboratory Hoods

    An efficient hood system is a requirement for all laboratories. Work that involves hazardous and/or noxious materials which are toxic, irritating, volatile or harmful shall be conducted within a laboratory hood.

    The primary purpose of a laboratory hood is to keep toxic or irritating vapors and fumes out of the general laboratory working area. A secondary purpose is to serve as a shield between the worker and equipment being used, when there is the possibility of an explosive reaction.

    1. Hood air velocity and velocity profile evaluations should be made at least annually and when ventilation changes, construction, maintenance, or normal wear and tear causes a change in the system. Contact OSU Environmental Health & Safety to perform this service.

    2. Hood ventilation systems are best designed to have an airflow of not less than 80 ft/min (linear) across the face of the hood, 100 ft/min (linear) for slightly hazardous materials, and 120 ft/min (linear) if toxic materials are involved. Flow rates of higher than 120 ft/min can cause turbulence problems and are not recommended. A mark or label shall be placed on the hood so the sash can be drawn to a point where 100 ft/min can be achieved. Guidelines for designing fume hood systems may be found in Industrial Ventilation, a Manual of Recommended Practice published by the American Conference of Governmental Industrial Hygienists.

    3. Avoid creation of strong cross drafts (100 fpm) caused by open doors and windows, air conditioning/heating vents, or personnel movement. Drafts will pull contaminants from the hood into the laboratory.

      100 FPM is generally not perceptible (100 fpm is approximately 3 mph, a normal walking pace). Air conditioning and heating vents plus personnel traffic all create airflows in excess of 200 FPM, often much higher. Therefore, care should be taken in fume hood placement and laboratory traffic pattern design to minimize activity near the hood in use.

    4. Hoods should be provided with audible/visual alarm to indicate when minimum or maximum face air velocities are not maintained or exceeded. A sign should be placed on the hood to indicate who to call should the alarm sound.

    5. Tempered makeup air should be supplied to rooms and/or to hoods to replace the quantity of air exhausted through the hoods.

    6. Incompatible exhausts should be ventilated separately with the exhaust being terminated a safe distance from the building.

    7. Exhaust fans should be spark-proof if exhausting flammable vapors and corrosive resistant if handling corrosive fumes.

    8. Controls for all services should be located at the front of the hood and should be operable when the hood door is closed.

    9. All laboratory rooms should have the air changed at a rate depending on the materials being handled and consistent with ASHRAE standards.

    10. Fresh outdoor air shall be supplied as outlined in ASHRAE standard 62.

  2. Biological Safety Cabinets

    Biological Safety cabinets are among the most effective, as well as the most commonly used, primary containment devices in laboratories working with bio-hazardous agents. The National Sanitation Foundation has developed standards for the design, construction and performance of vertical laminar flow biological safety cabinets (Class II). Utilization of this standard and list should be the first step in selection and procurement of a biological safety cabinet.

    Class I and II biological safety cabinets, when used in conjunction with good microbiological techniques, provide an effective partial containment system for safe manipulation of moderate and high-risk microorganisms. Both Class I and II biological safety cabinets have comparable inward face velocities (75 linear fpm) and provide comparable levels of containment in protecting the laboratory worker and the immediate laboratory environment from infectious aerosols generated within the cabinet. However, it has been recently shown that this 75 fpm face velocity may not adequately provide protection where laboratory activity and ventilation disturbance may significantly affect cabinet performance. Therefore, a minimum inward face velocity of 100 fpm is highly recommended.

    It is imperative that Class I and II biological safety cabinets are tested and certified in situ at the time of installation within the laboratory, at any time the cabinet is moved, and at least annually thereafter. Certification at locations other than the final site may attest to the performance capability of the individual cabinet or model but does not supersede the critical certification prior to use in the laboratory.

    HHS Publication No. (NIH) 99-8395, titled "BIOSAFETY IN MICROBIOLOGICAL AND BIOMEDICAL LABORATORIES", published by the Centers for Disease Control and National Institutes of Health, shall be consulted for classification, specifications, and laboratory design of biological safety cabinets and Microbiological and Biomedical laboratories.

  3. Specialized Local Ventilation

    Some instruments such as atomic absorption spectrophotometers (AA's) or inductively coupled argon spectrometers (ICP's) emit small quantities of hazardous substances during use. To prevent excessive accumulations of these materials, each of these instruments should be provided with an individual ventilation duct placed directly over the exhaust of the instrument. Manufacturer's recommendations should be consulted for cubic foot per minute requirements for each instrument.

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