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Technology Report

June, 2003

Siemens Industry, Inc. Page 1 of 10

Laboratory Ventilation Systems

Getting the Best Bang for the Buck

This report focuses on what type of ventilation

system can yield the most favorable life cycle cost

for a chemical laboratory with fume hoods. In many

situations it's not possible to provide a one size fits

all answer because of the many individual variables

involved. Laboratory activities extend from basic

chemistry instruction in teaching labs to advanced

research. Laboratory rooms vary in size and involve

an endless array of furnishings and equipment. All of

these factors impact the type of ventilation system

that will be most appropriate, as well as result in the

lowest life cycle cost. This report is intended as a

guide to selecting the type of ventilation system that

is likely to attain the lowest life cycle cost for a

specific type of laboratory and thus get the best

bang for the buck.

Ventilation System Characteristics

Laboratory ventilation standards require that a

laboratory's ventilation system must remain

functioning at all times when there are hazardous

chemicals within the room or a fume hood. Under

these situations, the laboratory room's ventilation

system may only be fully shut down for short periods

when necessary for testing, adjusting and servicing.

At all other times some amount of ventilation airflow

must be maintained. Thus, energy consumption

becomes a significant expenditure. Figure 1 shows

the relative e

nergy consumption characteristics of

the commonly applied types of laboratory ventilation

systems during the room's occupied and unoccupied

periods. An overview of each type of ventilation

system follows. See Table 1 for the recommended

ventilation sy

stem for various chemistry laboratory

applications.

Constant Air Volume (CAV) 1-

Position

A CAV 1-Position ventilation system provides a

constant ventilation airflow through a laboratory

room and its fume hoods during both the occupied

and unoccupied periods—24 hours a day and 7

days a week. It is the simplest system to design and

requires a limited amount of associated airflow

controls. It also requires a minimum amount of

knowledge and oversight by support (maintenance)

personnel. However, the tradeoff for this simplicity is

high-energy consumption since there is no provision

for reducing ventilation airflow during times when the

room is unoccupied or the fume hoods are not being

used. However, in certain limited applications, the

CAV 1-Position ventilation system can be the

optimum type of system.

Constant Air Volume (CAV) 2-

Position

A CAV 2-Position ventilation system provides two

levels of ventilation airflow through the laboratory

room and its fume hoods. It provides a higher

ventilation airflow rate when the laboratory room is

occupied and a lower amount when the room is

unoccupied. As with the basic CAV 1-Position

system, it is not a very complex design and requires

only a modest amount of associated airflow controls.

It requires some supervision and knowledge by

support personnel, and is often the optimum type of

ventilation system for certain types of laboratories.

Document No. 1

49- 980

Summary of content (10 pages)

PAGE 1
Technology Report June, 2003 Laboratory Ventilation Systems Getting the Best Bang for the Buck This report focuses on what type of ventilation system can yield the most favorable life cycle cost for a chemical laboratory with fume hoods. In many situations it's not possible to provide a one size fits all answer because of the many individual variables involved. Laboratory activities extend from basic chemistry instruction in teaching labs to advanced research.
PAGE 2
100 CAV-1 CAV-2 90 80 70 LAF-1 60 LAF-2 50 VAV 40 30 20 10 0 OC UN OC UN OC UN OC UN OC UN Figure 1. Comparative Energy Consumption Characteristics for Laboratory Ventilation Systems During the OC (Occupied) and UN (Unoccupied) Times of the Day. Low Air Flow (LAF) 1 & 2-Position Variable Air Volume (VAV) LAF 1 & 2-Position ventilation systems are basically CAV systems that achieve a lower ventilation airflow in conjunction due to the use of Low Air Flow 1 chemical fume hoods.
PAGE 3
Ventilation System Functions Regardless of the type of ventilation system they must all fulfill five requirements: 1. Maintain necessary fume hood exhaust airflow. 2. Provide sufficient room makeup airflow to balance off the fume hood exhaust and other exhausts. 3. Maintain sufficient total room exhaust airflow to achieve the room's minimum ventilation rate in air changes per hour 2 . 4.
PAGE 4
Table 1. Recommended Ventilation System Types for Various Chemistry Laboratory Applications. Type of Facility 1. Small Testing and Analysis Facility: Private laboratory or a small laboratory within a medical or commercial enterprise. 2. Small College: Undergraduate Chemistry Teaching Laboratory 3. Large College or University: Large Undergraduate and Graduate Chemistry Teaching Laboratories 4. 5. University Research Laboratories Mainly involves repetitive testing in a prescribed manner.
PAGE 5
1. Small Testing and Analysis Facility These laboratories are often small commercial operations with only one or two laboratory rooms. Technicians or workers conduct routine and repetitive testing that can involve daylong use of the fume hoods. Generally, the fume hoods are limited in size (5- or 6-feet wide units) and the testing requires only small amounts of non-toxic chemicals.
PAGE 6
. Government Research Government research laboratories include federally funded or federally sponsored research facilities. These labs tend to be very large facilities and often employ high level scientific personnel who conduct advanced research on space, defense, medical, biological, and in nuclear related areas. The fume hood sizes can vary widely and some may be quite large or of a special design. The time and usage pattern of the labs can vary extensively.
PAGE 7
Table 2. Comparison of Ventilation System Characteristics. Ventilation System CAV - 1-Position CAV - 2-Position LAF - 1-Position LAF - 2-Position VAV Benefits  Lowest first cost  High ventilation related sound  Easiest to design and implement  Highest energy consumption  Least impact on facility support personnel.
PAGE 8
Life Cycle Cost Analysis Life Cycle Energy Cost As previously stated, a life cycle cost analysis may be necessary to determine the most advantageous type of laboratory ventilation system in some situations. However, a particular type of system may still not be acceptable if the ventilation system's limitations (indicated in Table 2) are unacceptable.
PAGE 9
Table 3. Laboratory Annual Cubic Feet per Minute. System Type CAV – 1 & LAF - 1 Average Fume Hood & General Exhaust Cubic Feet per Minute (cfm) Calculation Procedure The average annual fume hood cfm is the normal constant fume hood exhaust cfm. The average annual general exhaust cfm is the normal constant general exhaust cfm. Step 1: Determine the laboratory's weekly occupancy percentage by dividing the normal Occupied Hrs/Wk6 by 168. (For 8 A.M. to 5 P.M. weekdays this typically is about 33%.
PAGE 10
Life Cycle Cost The annual energy cost along with the respective ventilation system's initial cost, maintenance costs, training costs, and other operating factors are then used in determining the life cycle cost for the ventilation systems being compared. Normally a life cycle cost should cover at least 10 years and oftentimes a few years longer. A constant air volume (CAV) system will usually provide the optimum expenditure based upon a 2 to 4-year life cycle.