Laboratory Standard & Design Guidelines – Stanford Environmental Health & Safety

1. The room should have mechanically generated supply air and exhaust air. All lab rooms shall use 100% outside air and exhaust to the outside. There shall be no return of fume hood and laboratory exhaust back into the building.

_{Good Practice per Stanford University EH&S}

_{Prudent Practices in the Laboratory 8.C, 8.D}

_{CCR, Title 24, Part 3, Section 505.3}

_{NFPA 45, Chapter 6-4.1}

_{ANSI/AIHA Z9.5, 4.10.3}

The air balance of the room cannot be adjusted unless there is mechanically generated supply and exhaust air.

2. Mechanical climate control should be provided.

_{Good Practice per Stanford University EH&S}

Per ASHRAE 55-1992, comfortable temperature range are defined as follows: Winter: 69-76 °F (at 35% RH); Summer: 73-79 °F (at 60% RH)
Electrical appliances often exhaust heat into a room (e.g., REVCO freezer, incubator, and autoclave). Failure to take this effect into consideration may result in an artificially warm working environment. Windows must not be opened for a cooling effect since the room air balance will be altered. A cool room must not be heated with a portable heater that may be a fire hazard.

3. Cabinetry or other structures or equipment must not block or reduce effectiveness of supply or exhaust air.

_{Good Practice per Stanford University EH&S}

Many supply diffusers and room exhaust room outlets are located along laboratory walls. Storage of boxes near these openings may obstruct the circulation of air and supply or exhaust air functioning.

4. Ventilation Rates

General laboratories using hazardous materials shall have a minimum of 6 air changes per hour (ACH). Exhaust ventilation shall be continuous.

_{2013 CMC section 403.7, Table 403.7}

_{2013 California Fire Code 5004.3}

_{2015 ASHRAE Handbook—HVAC Applications, Chapter 16}

The Fire Code requires exhaust ventilation at 1 cfm/ft2 of floor area for dispensing, use, and storage of hazardous materials in buildings operating above the maximum allowable quantity (MAQ). In a room with a 10 ft. ceiling, this equates to 6 ACH. The Mechanical Code requires a minimum exhaust ventilation rate of 1 cfm/ft2 for Educational Science Laboratories.

Upon consultation with EH&S, some labs may be candidates for reduced airflow changes (from 6 ACH to 4 ACH) when unoccupied during nonbusiness hours.
Many laboratory buildings now have laser rooms and rooms with analytic tools that do not require hazardous materials. Such rooms have been permitted with 3 to 4 ACH. Careful consideration should be given to not only current, but also future use of the laboratory as research needs change. Without adequate exhaust ventilation, future use of hazardous materials in the space will be restricted or require potentially costly retrofitting.

5. Laboratories must be maintained under negative pressure in relation to the corridor or other less hazardous areas. Clean rooms requiring positive pressure should have entry vestibules provided with door-closing mechanisms so that both doors are not open at the same time. Consult with SU Fire Marshal for design details.

_{ANSI/AIHA Z9.5 – 1992, 4.11.4-4.11.5}

As a general rule, airflow should be from areas of low hazard, unless the laboratory is used as a clean or sterile room.

6. Where appropriate, general ventilation systems should be designed, such that, in the event of an accident, they can be shut down and isolated to contain radioactivity.