1. Laboratory Ventilation:
Rethinking the Traditions
Ralph Stuart, CIH
Laboratory Ventilation Specialist
Dept. of Environmental Health and Safety
rstuart@cornell.edu
March, 2012

2. What is
Environmental Health and Safety?
Safety Compliance
Environmental
Health and Safety
Education Lab Productivity

3. What is a Lab?
• Labs are workplaces where people do
unusual things with hazardous materials
• Generic strategies are used to protect the
workers and the work:
1. Hazard replacement or downsizing
2. Facility design and operation
3. Worker training and oversight
4. Personal protective equipment and emergency
response plans
• This approach maximizes the ability of the
facility to host a variety of work.

4. Science and Safety
The challenge is balancing
contrasting priorities for facilities:
• The flexibility required by laboratory
work
• The definition and time needed by
building designers and operators to
plan and provide a safe facility
“Safe” can compete with
sustainability. For example, a
simple approach to this challenge is
to throw lots of air at the problem.

5. How Does Sustainability Fit Into This?
• Sustainability involves environmental aspects which
go “beyond compliance”
• Health and safety goes beyond compliance as well.
• Laboratory Ventilation is one of the bridge issues
between EHS and sustainability
• The increase and intensification of laboratory
research over the last two decades has led to
health and safety issues that go beyond traditional
lab safety models (chemical, biological and radiation
hazards as distinct concerns)

6. What is Lab Ventilation for?
The goal of lab ventilation is to control:
1.Space temperature
2.Fire hazards
3.Odors
4.Toxicity
5.Incoming dust levels (possibly)
6.Humidity (possibly)
- when dilution is the solution to pollution
The first method of ventilating labs
was opening windows.

7. Four Reasons Chemistry
Shouldn’t Smell
• It indicates a poor atom economy (a key principle
of Green Chemistry)
• Fugitive odors can mask more serious leaks
• Other people shouldn’t have to smell your work
• Do you want to be part of the index population for
your chemicals?

8. So, Fume Hoods:
The Sustainability Concern
• In terms of heating and air conditioning
energy impact, 1 fume hood = 3.5 houses

9. Fume Hoods: the EHS Concerns
• Face velocity: what’s the right one?
• The Ergonomic Challenge of Hood Work
• How much protection does a hood
provide? It depends.
Hood air flow did not or
would not have helped with
the 3 lab accidents cited
last fall by the US
Chemical Safety Board
(dermal toxicity, large fire,
explosion)

10. An Example of an
EHS / Sustainability Connection
• Variable air volume (VAV) hoods use electronic controls to
maintain 100 fpm face velocity as the sash height changes
• The controls balance supply and exhaust air to a space as
the hood sash is lowered to pull less air is out of the lab
• The electronics can also be connected to occupancy
sensors to reduce air flow when no one is present.

11. Ventilation outside the Hood,
Inside the Lab
• Air Quality: use 100% outside air to avoid
contaminants originating in the lab
• Air Quantity: When provided by the building,
measured in air changes per hour (ACH)
• At home, this is usually less than one ACH
• Highly ventilated animal rooms use 15-20 ACH
• The late 20th century approach: 10-12 ACH
24/7 in all labs

12. The 21 st Century Approach
• How many ACH are needed depends on what’s
happening in the room and how effective the
ventilation is
• Ventilation need can be driven by:
• Chemicals and other hazards
• Local exhaust requirements
• Temperature (solar and plug load)

13. Planning Lab Ventilation for Safety and
Sustainability
• For protection from chemicals, we have been
sorting Cornell labs into Control Bands
• We start with a standard minimum of 8 ACH when
the lab is unoccupied and 4 ACH when unoccupied
to control chemical concentrations
• We’ve been identifying many labs where we expect
6 ACH and 3 ACH to be adequate to control
chemical hazards.
• There are special cases outside these generic
categories (e.g. animal areas, BSL rooms)
• However, often exhaust requirements or temperature
management trumps chemical issues

14. Key Questions that have arisen
1.What safety value do we get out of the
air we supply to labs?
2.What’s difference between 8 and 6 ACH
in terms of controlling chemical
concentrations?
3.Can we go lower than 6 air changes per
hour?

15. Finding Some Answers
• We use carbon dioxide to measure and
compare chemical concentration decay
patterns within a laboratory

16. Key Results
• Major sources (that fill the room)
– Horizontal variation depends on furniture configuration
– Measured ACH is lower than building supplied ACH
• Minor sources (that don’t fill the room)
– More descriptive of lab events
– Measured ACH is higher than building supplied ACH
• The concentration decay is logarithmic, so
the time factor is better described as a “half-life”
(= ln(2)/ACH)

17. Concentration half life and ACH
8 ACH = half life of 5 minutes
6 ACH = half life of 7 minutes
4 ACH = half life of 10 minutes
2 ACH = half life of 21 minutes

18. EHS Interpretations
• To control chemical concentrations, lab air must be
single pass air.
• In lab situations, the difference in effectiveness between 6 and
8 ACH is small; the size of the room is as important as the
ventilation system in providing safety
• Chemical housekeeping, flammable storage cabinets, and local
exhaust are the best ways to control chemical “hotspots” in the
lab, for both safety and sustainability
• What about fume hoods?
• Hoods are popular because they address the first two points
when they are used.
• However, hoods often aren’t used (correctly) because they are
a significant ergonomics challenge.
• It’s not clear that they need as much air as they currently use.

19. Lab Energy Conservation Opportunities
• Identify hoods that can be decommissioned
• Reduce face velocity on hoods that can maintain
containment
• Set default ACH to 6 when chemical processes
allow
• Educate occupants about the role of lab ventilation
in a safe laboratory and why more isn’t better
• Start reducing electricity plug load to lower
ventilation requirements (Labs-21)

20. Today’s Lab Greening Moment?
http://www.nature.com/news/2011/110518/full/
473263a.html
[In the aftermath of the earthquake], the
University of Tokyo… cut peak power usage
by 30–40% by turning off lights and air-
conditioning, shutting down extra lifts, and
running energy-intensive experiments at night.
Researchers at the university say that their
low-energy lives are inconvenient, but largely
manageable... "The electricity shortage made
us realize that we can indeed save energy
easily by 10%, but that 30% cuts will impact
productivity in the longer term”, one said.

21. Questions?