Chapter 7: Risk Management Lecture 1 A. Section 7.1.1 Making Decisions About Safety 1. Incident 7.1.1.1 Nitric Acid and Ethanol Explosion 2. Introduction a. Scientists are constantly assessing risk and then deciding what to do about it b. Risk Management = steps taken to reduce risk c. Must weigh the potential “cost” of the hazard with the “benefit” of using the chemical, instrument, or technique, even if it is hazardous d. Decide how much time, effort, and money you will invest to make it an acceptable level of risk 3. What is Safe? a. Objective analysis of risk + Subjective decision about how much risk is acceptable b. Government regulates, to some extent, what is an acceptable level of risk c. Many decisions in the lab are outside of regulated activities d. Academic labs don’t have the same level of regulation as industry 1
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Chapter 7: Risk Management Lecture 1 A.Section 7.1.1 Making Decisions About Safety 1.Incident 7.1.1.1 Nitric Acid and Ethanol Explosion 2.Introduction.
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Chapter 7: Risk Management Lecture 1
A. Section 7.1.1 Making Decisions About Safety1. Incident 7.1.1.1 Nitric Acid and Ethanol Explosion
2. Introduction
a. Scientists are constantly assessing risk and then deciding what to do about it
b. Risk Management = steps taken to reduce risk
c. Must weigh the potential “cost” of the hazard with the “benefit” of using the chemical, instrument, or technique, even if it is hazardous
d. Decide how much time, effort, and money you will invest to make it an acceptable level of risk
3. What is Safe?
a. Objective analysis of risk + Subjective decision about how much risk is acceptable
b. Government regulates, to some extent, what is an acceptable level of risk
c. Many decisions in the lab are outside of regulated activities
d. Academic labs don’t have the same level of regulation as industry
i. Zero-Risk: perfect safety is required; no cost-benefit analysis allowed (rare)- 1938 “Delaney Clause” prohibits any chemical causing any cancer- 1988 EPA: changed to “de minimus” = too small to be concerned with- Would prohibit much of what academic lab chemists do routinely- Example: methylene chloride would be banned
ii. Balancing Laws: cost-benefit analysis plays a role in allowing activity
i. Safe Water Drinking Act: reasonably safe exposures
ii. More rational approach that allows much of what lab scientists do
iii. Technology-Based: zero-risk is not possible because current technology can’t achieve that level of purity/detection- Radon in homes can only be detected at a certain level- No use legislating a lower level than can be detected, even if desired
b. The Precautionary Principle
i. Hard (i.e. impossible) to prove a chemical is safe
ii. Showing it is “safe as far as we know” is possible
iii. Global Warming Example: negative outcome of not reducing CO2 emission is too onerous to wait for “proof”
B. Section 7.1.2 Laboratory Eye Protection in Introductory Labs1. Incident 7.1.2.1 Acid Splash in Eyes
2. Benefit of having eyes and eye-site is very large
a. Anecdotal stories of eye injuries are common in labs
b. Single most important safety rule: wear eye protection at all times
i. Incidents putting eyes at risk are likely to happen
ii. Broken glass and splashed liquids can’t be totally avoided
c. Why this rule is resisted
i. People don’t usually wear goggles outside the lab
ii. Easy to “not wear” goggles
iii. Goggles can impede vision
iv. Uncomfortable to wear, especially when you first start wearing them
d. Selective adherence to wearing safety glasses assumes you can tell what your neighbor is doing and/or assumes you can predict when splashes will happen
e. Strong acids/bases and many organic solvents are damaging to the eyes
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3. Types of Eye Protection
a. Impact Only safety glasses may not be able to protect against splashes
b. Chemical Splash Goggles are superior to impact only glasses and are recommended
a. Gloves for chemical protection are generally not good for thermal protection
b. Leather, terry cloth, asbestos gloves are used for hot objects
c. Gloves specifically for use with liquid nitrogen and/or dry ice are available- Thermal properties may not include impermeability- Liquid nitrogen may soak through and be trapped next to skin- Gloves are for handling object chilled by liquid N2, not the liquid N2 itself
F. Chemical Hoods in Introductory Labs1. Incident 7.1.4.1 Solvent Fire During Recrystallization
2. It is Best Not to Breathe Chemical Vapors
a. Many solvent, reagents, and even solids have significant vapor pressures
b. If you smell it, are you in danger?
i. People have wide ranges of odor thresholds (0.1-1000ppm for 10ppm odor)
ii. Odor fatigue: decreased sensitivity to odor due to continued exposure
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3. Chemical “Fume” Hoods
a. Regulations don’t require hoods, but they do require safe air in the lab
b. Basic Idea: air flows in only, and takes all vapors out with it
c. Sash slides vertically and/or horizontally
i. “Stops” designed to keep sash at acceptable level
ii. Can be over-ridden for full access to hood
d. Water, electricity, gas, compressed air, sink are common
e. Exhaust fan located on top of the building to pull air out
i. Negative pressure compared to lab
ii. Air pushes from lab, in, up, and out of hood
iii. Sensor with alarm detects air flow rate and sounds if too low
iv. “Make-up” air has to be supplied to the lab to equalize air pressure- Must be heated/cooled: extremely expensive to run Fume Hoods- Some hoods lower air flow when not in use- Always keep Sash closed when not in use: safer, less air flow = less $
4. Using the Fume Hood Safely
a. Use any time vapors, aerosols, gases, particulates, dust will be generated
b. Rule of thumb: Do it in the hood unless you know for sure it is safe out of the hood.
c. Make sure air is flowing: sound, detector, powder, pulling on a chemwipe
d. Reasonable face velocity for air flow = 100 feet/minute