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.

Good Practice per Stanford University 

7.  The air velocity volume in each duct should be sufficient to prevent condensation or liquid or condensable solids on the walls of the ducts.

Good Practice per Stanford University

The ACGIH Industrial Ventilation handbook (22nd edition) recommends a velocity of 1000- 2000 fpm.

8.  Fume hoods should not be the sole means of room air exhaust. General room exhaust outlets shall be provided where necessary to maintain minimum air change rates and temperature control.

Good Practice per Stanford University 

9.  Operable windows should be prohibited in new lab buildings and should not be used on modifications to existing buildings.

Good Practice per Stanford University

10.  Local exhaust ventilation (e.g., “snorkels” or “elephant trunks”), other than fume hoods, shall be designed to adequately control exposures to hazardous chemicals. An exhausted manifold or manifolds with connections to local exhaust may be provided as needed to collect potentially hazardous exhausts from gas chromatographs, vacuum pumps, excimer lasers, or other equipment which can produce potentially hazardous air pollutants. The contaminant source needs to be enclosed as much as possible, consistent with operational needs, to maximize control effectiveness and minimize air handling difficulties and costs.

ACGIH, Industrial Ventilation: A Manual of Recommended Practice, 23rd edition, or latest edition

Enclosure minimizes the volume of airflow needed to attain any desired degree of containment control. This reduces fan size, motor horsepower, make up air volume, and make up air conditioning costs.

11.  Hoods should be labeled to show which fan or ventilation system they are connected to.

Good Practice per Stanford University 

12.  No laboratory ventilation system ductwork shall be internally insulated. Sounds baffles or external acoustical insulation at the source should be used for noise control. 

Good Practice per Stanford University

Fiberglass duct liner deteriorates with aging and sheds into the space resulting in IAQ complaints, adverse health effects, maintenance problems and significant economical impact. Glass wool and refractory ceramic fibers are now rated as possible carcinogens by the National Toxicology program.

13.  Air exhausted from laboratory work areas shall not pass unducted through other areas.

NFPA 45, Chapter 6-4.3