Laboratory Ventilation:Rethinking the Traditions Ralph Stuart, CIH Laboratory Ventilation Specialist Dept. of Environmental Health and Safety email@example.com March, 2012
What is Environmental Health and Safety? Safety Compliance Environmental Health and Safety Education Lab Productivity
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.
Science and SafetyThe challenge is balancingcontrasting 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 withsustainability. For example, asimple approach to this challenge isto throw lots of air at the problem.
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)
What is Lab Ventilation for?The goal of lab ventilation is to control:1.Space temperature2.Fire hazards3.Odors4.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.
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?
So, Fume Hoods: The Sustainability Concern• In terms of heating and air conditioning energy impact, 1 fume hood = 3.5 houses
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)
An Example of an EHS / Sustainability Connection• Variable air volume (VAV) hoods use electronic controls tomaintain 100 fpm face velocity as the sash height changes• The controls balance supply and exhaust air to a space asthe hood sash is lowered to pull less air is out of the lab• The electronics can also be connected to occupancysensors to reduce air flow when no one is present.
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
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)
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
Key Questions that have arisen1.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?
Finding Some Answers• We use carbon dioxide to measure and compare chemical concentration decay patterns within a laboratory
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)
Concentration half life and ACH8 ACH = half life of 5 minutes6 ACH = half life of 7 minutes4 ACH = half life of 10 minutes2 ACH = half life of 21 minutes
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.
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)
Today’s Lab Greening Moment?http://www.nature.com/news/2011/110518/full/473263a.html[In the aftermath of the earthquake], theUniversity of Tokyo… cut peak power usageby 30–40% by turning off lights and air-conditioning, shutting down extra lifts, andrunning energy-intensive experiments at night.Researchers at the university say that theirlow-energy lives are inconvenient, but largelymanageable... "The electricity shortage madeus realize that we can indeed save energyeasily by 10%, but that 30% cuts will impactproductivity in the longer term”, one said.