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
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4. Health and Safety Laws and Regulations
a. Categories of safety laws and Regulations
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”
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5. Risk-Benefit: Making Informal Decisions in Lab
a. Risk-Benefit = how much risk are we willing to accept to achieve goal
b. Cost-Benefit = how much money/effort are we willing to invest to achieve goal
c. Benefits to Scientists of their work: money (grants, salary), fame, satisfaction,
knowledge, “immortality”
d. Risk to Scientists: statistically proven incidents of explosion, fire, toxicity, etc…
e. Time = Money in the lab: scale up reaction to do once rather than ten times
f. Risk is not just for researcher, but everyone else in the lab as well
g. Faculty/Manager may choose differently than the student/employee
h. Information in the class is to help you make an informed decision
6. Bhopal Tragedy: an example of poor risk management
a. Methyl Isocyanate (MIC) produced in Union Carbide plant in Bhopal, India
b. Stored in 40-ton and 15-ton tanks—valve failed and released 40 tons
c. Electricity to refrigerate (bp = 39 oC) turned off to save money
d. Neutralizing scrubber had been turned off
e. Water-jet used to capture MIC didn’t have enough pressure
f. Safety equipment and procedures lacking because not required in India
g. Thousands died in a preventable accident
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B. Section 7.1.2 Laboratory Eye Protection in Introductory Labs
1.
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
c. ANSI (American National
Standards Institute)
d. ASSE (American Society of
Safety Engineers)
e. ASSE Z87.1 stamped goggles are
acceptable for chemistry labs (impact)
f. Tight seal around the face can
prevent splash from running into eye
g. Vented (indirectly) goggles are
recommended to avoid fogging up
(poor vision is also not safe)
h. Comfort is important
i. More likely to wear
ii. May have to try them on
i. Eye Protection beyond Chemical
Splash Goggles not likely needed
in Introductory Labs
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4. Contact Lenses in the Lab
a. NIOSH Recommends no contact lenses in the lab—1970’s
i. National Institute for Occupational Safety and Health
ii. Vapors and/or liquids could be trapped up against the eyeball
iii. Washing away chemical impeded by the lenses
b. 2005: NIOSH recommends workers be able to wear contacts
c. Wearing Contacts does not remove requirement of Chemical Splash Goggles
d. If splashed, remove contacts as soon as possible
e. Co-workers or emergency responders need to know you are wearing them
5. Can you Ever “Not Wear” goggles in the lab?
a. If no chemicals are in the lab—library assignment or computer lab work
b. Doing calculations: only if everyone else is done using chemicals as well
c. Get goggles out of your drawer as the first thing you do in lab
6. Can you Ever wear Impact only Goggles/glasses?
a. If no liquids are used in the lab
b. Solid chemical can also be “splashed”, spilled, or left as dust in the air
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C. Section 7.2.1 Advanced Labs and Eye Protection
1.
Incident 7.2.1.1 “Bumped” Solution
Safety Glasses and Visitor’s Glasses
a. If zero risk of splashing, safety glasses with side shields may be acceptable
b. Safety glasses with prescription lenses are sometimes available
c. Safety glasses sometimes fit over prescription glasses
d. Not recommended for working in most chemistry lab situations
3. Beyond Chemical Splash Goggles
a. Lab jackets cover most skin, but faces and hands are still exposed
b. If you assess a high likelihood or serious risk, going beyond goggles is possible
c. Face shield: cover the rest of your face and neck
i. Even experienced chemists may have reactions out of control
ii. Use during procedures that are particularly explosion prone
iii. Better to overprotect than to under protect
iv. Still have to wear chemical splash goggles underneath the shield
d. Hood Sashes: keep reactions behind multiple layers of impact/splash protection
Keep the sash closed as the default position: if you’ve got it, use it
2.
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4. Portable Safety Shields
a. Particularly dangerous reactions should be further shielded by portable shield
a. High pressure reactions: polymerization reactions, hydrogenations
b. Sealed tube reactions
c. Cumbersome, but gives you an extra line of protection
5. Eye Protection for UV and Visible Light
a. UV light can damage eyes and destroy vision
b. Very bright visible light can also damage eyes
c. Safety glasses with UV protection included can be purchased if routinely exposed
d. Get information from co-workers or supervisors about risks in your lab
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D. Protecting Your Skin
1.
Incident 7.1.3.1 and 7.1.3.2
2.
Barriers to Chemical Exposure
a. Bare skin in the lab is a bad idea: shorts, skirts, tank tops, etc…
b. Wear clothing that puts a barrier between your skin and chemicals: think ahead
c. Lab coats and aprons can provide an additional barrier and protect your clothing
d. Shoes should be closed toed: spills go down (where your feet are)
e. Exception: chemical soaked clothes—take them off and get under safety shower
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3. Protecting Your Hands: Appropriate Gloves
a. Cuts and Punctures
i. Not completely avoidable when working with glass, sharps, etc…
ii. Dispose of broken glass in proper container: janitors shouldn’t get cut by trash
iii. Learn correct technique for needles, etc…; dispose of properly
b. Chemical Exposure
i. Hands are most likely place to be exposed
ii. Work carefully, rather than relying on gloves to protect you
iii. Change gloves if exposed and wash hands frequently
c. Choosing the right glove
i. No single glove is right for all chemical exposures
ii. Features: size, thickness, cuff length, material made of
iii. Glove Protection Charts are available on-line for different glove materials
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http://www.safetyinfo.com/guests/Chemical%20Glove%20Selection.htm
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d. Gloves for Introductory Labs
a. Any glove is adequate for solids
b. Acids and Bases may damage skin, but most gloves are adequate
c. Nitrile gloves give additional protection against many organic solvents
e. Latex Gloves
a. Latex is a natural rubber from rubber trees
b. The spread of HIV ushered in widespread use of latex gloves
c. Allergies to latex are common: skin irritation, bumps, sores; even death!
d. Nitrile gloves have now become standard replacement for latex
f. Glove Details
a. Disposable gloves are usually 0.005 inches thick
- Good dexterity
- Not that good for punctures: still have to respect sharps
b. Most disposable gloves available in S, M, L, XL
- Right fit is important to safety
- Need dexterity without slipping around in the glove
g. Taking off disposable gloves
a. Contaminated gloves should be removed and replaced
b. Must not contaminate yourself by contacting the outside of the glove
c. Reverse peel the gloves off, touching only the wrist
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4. When to Wear Gloves
a. You do not need to constantly wear gloves
b. Wear them when doing tasks that involve hazardous chemicals
i. Gloves: conc. acid, phenol, benzene, new research compound, base bath
ii. No Gloves: operating instrument, using keyboard, weighing NaCl
iii. Biology: gloves are mandatory with blood borne pathogens
5. Handling Hot Glassware
a. Insulated gloves are available for hot and cold objects
b. Disposable rubber gloves are not appropriate
c. Use tongs or forceps that were designed for the type of glassware you are handling
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E. Skin Protection in Advanced Labs
1.
2.
Incident 7.2.2.1 Fatal Exposure through Inappropriate Gloves
More Chemicals in Advanced Labs Mean More Hazards
a. Advanced labs use more toxic chemicals, hotter apparatus, and cryogens routinely
b. Lab coats are more prevalent and necessary in this environment
c. Contact Dermatitis from continued exposure to solids/liquids is more likely
3. Testing gloves for Chemical Permeability
a. Permeation = penetration by chemicals
i. Breakthrough time = first appearance
ii. Rate of transfer = speed of permeation
b. Degradation = destructive change in glove
c. These two don’t have to be related; a chemical
could permeate a glove without degrading it
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4. Choosing the Appropriate Glove for Advanced Labs
a. Latex:
i. Thin, flexible, inexpensive
ii. Good against aqueous solutions, dilute acids and bases
iii. Not good against most organic solvents
iv. Easily punctured or torn
b. Nitrile: the general purpose glove of choice in most chemistry labs
i. Disposable versions have similar flexibility and feel of latex: no allergies
ii. Synthetic polymer is much more puncture/tear resistant than latex
iii. Good against most organics, aqueous solutions, acids and bases
iv. Can be degraded by: ketones, aldehydes, esters, aromatics
c. Laminates = combining layers of different materials
i. “Silver Shield” gloves reportedly protect against 280 different chemicals
ii. Best protection; 60 x more expensive than nitrile disposables
iii. Disadvantages: expense, dexterity, mechanical damage
5. Heavy Duty Gloves: Thicker is Better
a. Thick Nitrile gloves or Butyl gloves can be used in obvious corrosive/toxic cases
b. Cleaning out the base bath; making/using aqua regia, etc…
c. 0.025 inches thick is common, giving very good puncture/tear resistance
d. These are not disposable and may be long enough to cover entire arm
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6. Gloves for Extreme Temperatures
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
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F. Chemical Hoods in Introductory Labs
1.
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
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e. Set up your apparatus fully before adding any chemicals: put sash up until ready
f. Once chemicals are added, keep sash at the stop, never more than half-way
5. Factors Influencing Hood Performance
a. Airflow Velocity: too high can be bad because it creates turbulence
b. Clutter in the hood impedes flow of air as designed and may allow contamination
c. Disturbing the air in front of the hood can “pull” out vapors
d. All apparatus 6-inches back from sash and up on 2-inch blocks
e. Keep the sash closed: mechanical shield as well as vapor removal
6. Keeping the Hood Safe
a. Don’t store chemicals or waste in the hood
i. People end up using the bench instead
ii. Glassware and containers impede proper air flow
b. Test air flow velocity on a yearly basis
c. Do not use a hood that is not flowing, or not flowing properly
i. You think you have protection, but you don’t
ii. Probably worse than using no Fume Hood at all
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G. Containment and Ventilation in the Advance Lab
1.
Incident 7.2.3.1 Osmium Tetroxide (OsO4) Exposure
2.
Sublimation Hazards
a. Sublimation = solid going directly to gas
b. Expectation is that liquids and gases would be vaporizing
c. Readily Subliming Solids can have significant vapor pressure
i. Dry ice (CO2)—cryogen used in cooling baths; not particularly hazardous
ii. Iodine (I2)—solid halogen used in TLC plate development, Grignard Reaction
Relatively Toxic by Inhalation; use fume hood
iii. Naphthalene = moth balls
iv. Dichlorobenzene = toilet deodorant
d. Small, symmetric, neutral molecules are most likely to sublime easily
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3. The Lab Room
a. Turnover rate (air exchange rate) = rate entire volume of air replaced
i. OSHA recommends Turnover rate = 6-12/hr (98% air replaced in one hour)
ii. Chemical Fume Hoods generally increase this due to constant air removal
b. Even in a high-turnover room, pockets of unmixed air can exist
c. Lab HVAC systems designed to keep negative pressure in the lab
i. Keeps air movement out of hall and into the lab when doors are opened
ii. Keeps vapors in the lab, rather than allowing them to spread
iii. Don’t leave doors open or windows open; this will defeat the design
4. More on Fume Hoods
a. Air flow designed to keep vapors out of the lab
i. Smooth air foil at front face allows air to move
across hood floor to capture heavy-than-air vapors
ii. Rear baffles adjust for low/med/high exhaust
b. What if you don’t have built-in air flow detector
i. Vaneometer = hand held meter measures air flow
ii. Inexpensive; gives numerical data (25-400 ft/min)
c. Horizontal sash section can allow provide complete body and face protection, while
allowing you to use both hands inside the hood
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5. Specialized Chemical Hoods
a. Perchloric Acid (HClO4) Hoods
i. Perchloric Acid used for digestion of organic material
ii. Metal and Organic Perchlorate salts can be shock sensitive explosives
iii. Interior of the hood must be non-reactive (stainless steel) with sealed seams
iv. Built-in wash-down equipment included to remove residue after use
v. Exhaust system must be independent (“regular” hoods are often tied together)
b. Radioactive Materials Hoods
i. Specially designed hoods allowing for easy decontamination
ii. HEPA and charcoal filters at exhaust to prevent release of radioisotopes
iii. Usually stainless steel
6. Gloveboxes
a. Atmosphere is entirely contained and controlled
i. No O2, H2O or Containment of toxic, radioactive, pathogens
ii. Use Argon, purified N2 as atmosphere, oxygen and moisture sensors
iii. Recirculation of atmosphere through a catalyst to remove O2, H2O
iv. Evacuatable chamber allows removal of air prior to entry into glovebox
v. Gloves allow manipulations—the weak link: puncture, degrade, etc…
vi. Toxic/radioactive/pathogens: rely on filtration of exhaust
b. Get help from an experienced user before attempting to use
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7. Other Containment Systems
a. Local Exhaust systems
i. Far inferior to a fume hood
ii. Overhead “Snorkel” systems with negative pressure exhausting outside
iii. Examples of use: AA, GC, Mass Spectrometer
iv. Can’t guarantee 100% removal of gases
b. Boxes around a work area with exhaust
i. Sometimes place around a balance to remove fumes
ii. Not very reliable; generally homemade (move balance to hood)
c. Ductless Hoods
i. Stand alone hoods that filter rather than exhaust vapors
ii. If not absorbed, the vapor goes right back in the room
iii. Never use for volatile, flammable, or toxic chemicals
iv. NOT RECOMMENDED
d. Biological Safety Cabinets
i. HEPA filters remove pathogens
ii. Air is returned to the room
iii. Not designed for chemical filtration
iv. Discussed in detail in Ch 4
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