HOUSEKEEPING

__Facility, furniture, work areas, sinks and equipment are generally clean

__Items not in use are stored away

__Door viewing panel not covered or blocked

__Overhead storage is minimized and restrained from falling

__Exits not blocked

GENERAL LABORATORY SAFETY

__Accurate Hazard Warning Placard posted at entrances

__Laboratory secured against unauthorized entry

__Warning labels on refrigerators and freezers (Radioactive, Biohazard, etc)

__Warning signs and labels at designated work areas (Radioactive, Carcinogens, etc)

__HKUST Safety Manual available

__Lab-specific MSDSs available (If not, ask help from CLS or HSEO)

__Equipment maintained in good condition, preventive maintenance program in place

__No food or drink in work area

PERSONAL PRACTICES CHEMICAL STORAGE AND HANDLING

__Lab coats and safety glasses available and used when required

__Protective equipment available and used when required. ( eg. Face shields, aprons, chemical resistant gloves, cryo-gloves )

__Gloves removed before handling telephone, door handle or leaving laboratory

__No eating or drinking in work area

CHEMICAL STORAGE AND HANDLING

__Chemical inventory present

__No excessive chemical stock

__No expired chemicals

__Chemical containers properly labeled

__All chemical containers in good condition and closed properly

__Only compatible chemicals are stored together ( eg. no HNO3 with EtOH, oxidizers with flammable solvents)

__Polyethylene trays for separate storage of acids and bases

__Secondary containment for stored chemicals as necessary

__Highly toxic or carcinogenic chemicals identified and locked

__Peroxide formers dated upon receipt and opening, and not stored beyond expiration

__Flammable liquids stored in flammable cabinet or explosion-proof refrigerator

__Flammable liquids stored away from sources of heat and ignition

COMPRESSED GAS CYLINDERS

__Gas cylinders secured to structural component of the building

__Gas cylinders stored in protected, well ventilated, and dry locations away from heat and combustible materials

__Compressed gas cylinders fitted with appropriate flow regulators

__Gas tubing of suitable material and pressure rating secured and in good condition

__Labels attached and show correct use status

__Flame arrestor installed in supply line of flammable gas

HAZARDOUS WASTE

__Correct chemical waste containers for each liquid chemical waste

__Secondary containment for liquid chemical waste ( ask HSEO or CLS for advise)

__Waste log sheet available and properly filled in after each addition of waste

__No more than 50 litres of hazardous waste stored in the laboratory

__Broken glass/sharps containers are used

__No intentional disposal of chemicals by evaporation into a fume hood

__ended 3 November 1995

LABORATORY FUME HOODS AND VENTILATION

__Certification current (check sticker on front panel)

__Air flow indicator (green light) and warning buzzer properly functioning

__Front sash at appropriate level when hood is in use / not in use

__Biological Safety Cabinet certification current (check sticker on front or side)

__If hood is not in working condition a “DO NOT USE” sign should be posted on the sash.

__All work generating vapor, fume, or aerosol performed in fume hood

__Fume generating apparatus at least 20 cm from face of hood

__Storage of chemicals inside the hood minimized and containers kept sealed

__Local exhaust units used where hoods are not suitable

__Negative pressure in laboratory not disturbed by constantly opened door or ceiling tile

__Ventilation inlets and outlets not blocked

RADIATION SAFETY

__All radiation workers registered with HSEO

__Thermoluminescent Dosimeter (TLD) worn by all radiation workers

__Current radioactive material inventory available

__Radioactive material properly stored and locked

__Sufficient shieldings for radiation work available

__Calibrated radiation survey meters available

__Periodic facility contamination evaluation performed and documented

__Radioactive wastes properly stored, according to physical forms and radionuclides

__Radioactive waste log sheet filled out properly

ELECTRICAL SAFETY

__All electrical circuits are three-wire with earthing

__Warning labels put on high voltage equipment

__Electrical panels/switch box not obstructed

__Extension cords not used as permanent wiring

__Wiring and plugs Proper and no frayed wires

__No circuits overloaded with extension cords or multiple connections

__Apparatus equipped with earthing or double insulated

__Heating apparatus equipped with redundant temperature controls

EMERGENCY PREPAREDNESS

__Emergency procedures and Fire Escape Route posted

__Emergency 8999 number sticker on telephone set

__First aid materials available and in good condition

__Emergency ventilation switch accessible and functional

__Chemical spill kit and cleanup procedures available

__Safety showers and eye washes easily accessible

__Fire extinguishers, fire blankets and sand buckets available

__600mm vertical clearance maintained from sprinkler heads

__Hazardous materials not stored along exit route

__Exit signs readily visible

Notes

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Radioactive Substances

Although the Hong Kong Radiation Board has granted HKUST an exempted from their licensing requirement, we still need to keep records of our use of radioactive materials in order to comply with the other Radiation Board requirements which are still in place. Reporting quantities of radioactive materials based on budget requests and bills of lading is not an acceptable way to accomplish this task. HSEO recommends numbering each container, and logging the use times, quantities, and final disposition. This will allow each department to keep better track of their radioactive substances and will enable HSEO to provide the Radiation Board with reliable data concerning our radioisotope use pattern as well as disposal.

Food in the Lab

Chapter2, section E.1 "Laboratory Hygiene" of the HKUST safety manual states "Food and drink should not be stored or prepared in laboratories or chemical storerooms. All food and drink should be consumed in specially designated areas such as canteen or pantry."

Dangerous Goods

The Hong Kong Fire Services Department has issued dangerous goods (DG) licenses to HKUST to store various dangerous goods on campus. The licenses carry certain requirements concerning the construction and fitting of the DG stores as well as setting limits on the amount of DGs which can be stored at any one time. The FSD DG regulations allow storage of exempted quantities of DGs without a license. These small quantity exemptions allow storage of DGs in labs and corridors within the campus. Persons stoning DGs should contact HSEO to ensure that they are staying within the exempted quantity limits. Dirty corridors are a popular location to site flammables cabinets, but the corridors are not licensed DG stores so that total quantities within a single corridor must not exceed the FSD exempted amounts.

Personal Protective Equipment (PPE)

The best case of personal protective equipment is to be in a situation where none is required. However, in a teaching and research institution with a wide range of activities, there are bound to be hazardous situations which will require some form of personal protective equipment. The PPE may be intended to protect you from chemicals which are poisonous, irritating, corrosive, carcinogenic, or to protect from hearing loss due to excessive noise levels. There are many situations where multiple forms of PPE will be required. Therefore, it is important that you are aware of all of the possible hazards and use all of the appropriate PPE. HSEO is available to assess the need for PPE as well as to recommend the appropriate equipment.

Eye Protection

Contact lenses should not be worn in the laboratory, and especially not when working with hazardous chemicals. The lenses can trap particles against the eye, and plastic lenses can absorb and be damaged by airborne solvents and can also prolong chemical contact with the eye. Furthermore cases have been reported where the lenses have become bonded to the eye due to the interaction of the plastic lens with airborne solvents.

Proper eye protection should be worn whenever you are working with hazardous chemicals such as organic solvents, acids and bases. Eye protection should also be worn when performing operations which can produce airborne particles which could damage the eye such as grinding, torching, chiselling, etc. Exposure to certain types of lasers present the risk of serious and permanent damage to the eye and special type of safety glasses are required.

There are a wide variety of products which afford eye protection including safety glasses, goggles, and shields. It is important to select the most appropriate eye protection for each particular task.

Lab Coats and Protective Apparel

Lab coats, safety goggles, face shields, gloves, etc. should be worn by personnel handling hazardous materials and should be appropriate for the hazard level. Contaminated clothing should be removed and cleaned or disposed of a necessary. It is important to remove contaminated clothing in such a way so that you don't contaminate yourself.

When handling toxic or hazardous chemicals, it is critical to select gloves that are made of a material which is impervious to the particular chemical. For instance organic solvents such as alcohols will penetrate through surgical gloves made of thin latex. There is no glove which is impermeable to all substances and there are some compounds which will penetrate any glove material. However, there are gloves which are more impermeable than others and it is a matter of limiting the contact time and changing the gloves as necessary. Chemicals which are soluble in non-polar compounds such as carbon tetrachloride and benzene and insoluble in polar compounds such as water are skin permeable.

The following are some general guidelines for selecting gloves:

1. Thick latex gloves such as are used around the home are suitable for general purposes.
2. Thinner latex gloves such as surgical gloves are suitable for use with aqueous solutions, tissue culture, and most dry chemicals. Polyethylene or polyvinyl chloride gloves are not recommended for culture work because of reports of virus penetration of the gloves.
3. Gloves should be selected that are long enough to cover the cuff of the lab coat to prevent contamination of the wrist.
4. Two pair of gloves should be worn when working with extremely hazardous materials including carcinogens and unbound radio iodine. The outer gloves should be changed when contaminated. Gloves used for this type of purpose should never be reused.
5. Powder free gloves may be desired if there is a concern for experiment contamination or worker allergy.
6. Gloves should not be worn when working with equipment with moving parts which are in motion due to the physical hazard of catching them in the equipment.

There are other hazards to the hands including thermal bums due to extremely hot or extremely cold conditions. There are a wide variety of gloves and HSEO is available to help in the selection process.

Respirators

Inhalation of air containing hazardous materials whether is a dust, fume, vapor, mist, fog spray or some other aerosol can result in lung disease and even death. The best way to prevent such exposure is to capture the contaminant at the source via some type of ventilation or exhaust system such as fume cupboards or biosafety cabinets. The total elimination of exposure via these methods is not always possible so that situations arise which require some level of respiratory protection.

It is extremely critical to select the correct respirator for the operation involved. The level of respiratory protection ranges from paint/dust masks to supplied air.

1. Half-face, negative air, respirators with filter cartridges are the most widely used type of respirator, aside from disposable dust masks. When using this type of respirator it is important to select cartridges which are suitable to the type and concentration of airborne contaminant. It is also important to understand the limitations of this type of respirator, such as the fact that it is totally ineffective in an oxygen deficient environment and use in such a situation could lead to death.
2. Supplied air respirators are effective and required for use in oxygen deficient environments. At HKUST situations calling for the use of supplied air are emergency situations only, and require special breathing apparatus (BA) training.

Hearing Protection

Unprotected exposure to excessive noise levels can result in temporary or permanent loss of hearing. Most elevated noise levels on the HKUST campus are limited to plant operations such as the seawater pump station and the chiller plant. SEPO performs noise surveys to assess levels of noise and make recommendations for corrective and or protective actions. The campus Health Center is equipped to perform audiometric testing.

(This article is taken from August/93 issue of SafetyWise )

Laboratory personnel working with biologically hazardous materials must be familiar with using Biological Safety Cabinets (BSC). When used properly, a BSC is one of the ways to protect the research materials from being contaminated; it also protects the worker from exposure to the biological material. Sometimes, a Bunsen burner is used inside a BSC for sterilization purposes, such as flaming the inoculating loop or the mouth of a bottle. However, one must be cautious when choosing the type of burner to be used inside a BSC, or deciding whether an open-flame burner is necessary at all.

The Incident

Recently, there was an incident in a laboratory on our campus. A researcher left a lit Bunsen burner inside a BSC and walked away. The sash of the BSC was closed at the time. A BSC normally recirculates about 70% of the air with 30% of the air goes out the exhaust. Having the sash closed provided no supply of fresh air, and thus, no exhaust was leaving the cabinet. Heat within the BSC built up quickly. The incident was discovered by SEPO staff only after the flame had burned for a period of time. The BSC retained so much heat that it was hot to the touch on the outside. It could have been more serious if the incident was not discovered at that time.

Lessons Learned and Recommendations

There were two things to be learned from this incident NEGLIGENCE and INAPPROPRIATE CHOICE OF EQUIPMENT can lead to disaster. We should always bear in mind that experiments with potential danger should never be left unattended, especially when an open flame is involved.

On the other hand, a standard Bunsen burner is only appropriate for open-bench usage. Inside a BSC, a Touch-O-Matic Bunsen Burner should be used. This type of burner is built in a way that a platform is connected to the burner itself. Aflame is only produced when the user's hand rests on the platform. When the user's hand moves away, only a pilot light burns. Touch-O-Matic Bunsen Burner also serves the purpose when a continuous flame is needed, the platform only needs to be pressed and slightly twisted. Consequently, the risk of leaving a full flame on by negligence is reduced. From an environment point of view, it conserves gas consumption as well. We urge the Biological Safety Cabinet users to take note of this message and choose the appropriate type of Bunsen burner for your BSC.

Please also note that as a general rule, one should avoid using burners inside a BSC all together, if possible. First of all, the ascending heat current generated from the flame will work against the descending air flow which acts as an air curtain to prevent the escape of material inside the cabinet and entry of material from the outside. Secondly, air coming down from the HEPA filter should be sterile. When used properly, the working space inside the BSC should also be sterile. Therefore, it should not be necessary to use a flame inside the cabinet for sterilization. In the case that streaking loops are to be sterilized inside a BSC to prevent cross-contamination of biological materials, an electrical incinerator is recommended.

(This has been taken from Feb, 1996 issue of  SafetyWise)

Electrophoresis, a technique which separates molecules based on their electrical charge, is frequently used in today's laboratories. The increasing popularity of electrophoresis brings up issues of electrical safety and gel disposal.

Shocking News

One common feature of many medical research labs is electrophoresis equipment. In any type of electrophoresis - disc, gel, isoenzyme or lipoprotein - there is movement of particles in an electric field toward one or the other electric pole, cathode or anode.

It is commonly believed that there is little hazard in electrophoresis apparatus use except when operating at high voltages required for procedures such as DNA sequencing. However, even agarose gel electrophoresis operating at 100 volts can cause a lethal shock at a current of 25 milliamps. Precautions to prevent electrical shock and using electrophoresis apparatus safely include:

• Turn the power off before connecting the electrical leads.
• Connect one lead at a time using one hand only.
• Insure that your hands are dry while connecting the leads.
• Keep the apparatus away from sinks or other water sources.
• Turn off power before opening lid or reaching inside chamber.
• Don't override safety devices.
• Don't run electrophoresis equipment unattended.

 

Electrophoresis Gels : Are they Hazardous ?

A discussion of electrophoresis would not be complete without mentioning the gels and the chemical hazards they can carry.

Many researchers believe the gels are harmless and, while agar itself may be, the additives used are often hazardous. For example, ethidium bromide, commonly used to visualize nucleic acid, is a mutagen and should be handled with caution, even when mixed in the gel. In addition, various catalysts, denaturants, stains and solubilizing agents contain a variety of chemicals, including formamide, phenol and acrylamide. This can result in unforeseen results. For example, a Canadian university analyzed agarose gels and found heavy metals, even though no metals or metal-containing reagents were used in the gel preparation. Presumably, the metals leached from the electrical contacts while the electrophoresis happened.

Acrylamide also poses significant hazards. It is a potent nerve toxin in its unpolymerized state, although it is less toxic when polymerized. In making gels, however, the polymerization process is never fully complete, and small amounts of acrylamide monomer are always present.

For these reasons, researchers should handle gels with caution,  wearing gloves and washing their hands often.Also,these materials should be disposed of as hazardous waste. Collect your gels in a leakproof container and attach a hazardous waste tag to it when it is full. Risk Management will help you send this waste to its proper disposal site.

In HKUST, electrophoresis gel with potential hazards is collected at laboratories as hazardous waste by HSEO. Users should put such gel in double layer of plastic bags inside a disposable box with clear indication of the content. HSEO staff will affix proper hazardous waste labels to the containers and remove the waste during our weekly waste collection run. 

(Information partially extracted from University of Vermont 'Safety Notes'. Winter 1993.)

Incident One

Last November, a lab worker performed an experiment which involved the heating of N,N-Dimethylformamide (DMF), a chemical with evidence of mutagenicity and carcinogenicity. The procedure is normally conducted in a fume cupboard since a small amount of DMF vapor, which is toxic and has a strong odor, would be produced . However, the fume cupboards in that lab were occupied by other experiments at that time. Considering that the scale of the experiment was rather small, using only several milliliters of DMF, the student decided to perform it on the open bench-top. He kept the lab doors closed to try to keep the odor from escaping his lab. The experiment went on for some time, and when it was finished, the student left for dinner.

In the evening, another lab worker came to work in the same lab. He did not know about the DMF experiment in the afternoon. When he entered the lab, he immediately noticed a strong smell which he thought was some kind of amine-compound, which is toxic. He found the smell was still coming from a experiment set in a heated water bath. He shut off the water bath and activated the emergency ventilation button in the lab.

With the activation of the Emergency Ventilation, the security control center evacuated all personnel from the entire 7th floor. SEPO emergency response team was called in to evaluate the situation. Since the exact nature of the incident could not be readily determined and it took some time to locate the people responsible for the experiment in question, the entire 7th floor was closed down for approximately two hours.

Lessons learned and comments.

• Procedures involving volatile and toxic chemicals must be handled in the fume cupboards. Supervisors are responsible for ensuring that all chemical handling activities under his/her management are done according to established procedures.
• It should also be mentioned that the response by the second lab worker was correct and commendable. When there is a suspected leak of toxic chemicals, activate the emergency ventilation system immediately, report it, and leave the affected area . Do not put yourself at risk.

 

Incident Two

One evening in last October, a lab worker took a bottle of Acrylamide solution from the refrigerator and put it onto a hot plate, intending to heat it up. The bottle was a regular 500ml brown glass bottle which cannot withstand much heat. Upon heating it broke, and the contents was spilled onto the hot plate, creating a cloud of steam. Knowing that the acrylamide monomer is neuro-toxic and carcinogenic, and that the room was filled with the steam from the acrylamide solution, the student activated the emergency ventilation button in the lab.

Following standard procedure, the security control center evacuated all personnel from the affected floor and called in the HSEO emergency response team to clean up the spilled chemical. It eventually took three hours to return the affected floor to normal.

Lessons learned and recommendations:

• Beakers and flasks found in laboratories are usually made of borosilicate glass, the most common brand is Pyrex. Borosilicate glass is expensive but it is resistant to thermal shock since it has a relatively low thermal expansion coefficient ( 3.3 x10-6 /C ). Regular bottles and containers are mostly made of inexpensive soda lime glass, which has a relatively high thermal expansion coefficient (9.2x10-6 /C). They can easily break when subject to temperature shocks, so they should only be used as containers, not as vessels for heating.
• Always use the correct ( preferably the best ) equipment for the job. ( Pyrex container and a water-bath in this case )
• Allow enough time for preparation before conducting an experiment. Never rush an experiment by turning up the heat.
• When toxic chemicals are involved, allow as wide a safety margin as possible.

 

Incident Three

One morning in November, as a lab technician was checking the chemical cabinets in the labs, he was surprised to find several bottles of chemicals in a cabinet not designated for chemical storage. He did not know about the chemicals until then and did not know who had put the chemicals there. There were 2 bottles of concentrated hydrochloric acid, one bottle of concentrated nitric acid, one bottle of concentrated sulfuric acid, a bottle of ethyl alcohol and a bottle of glycerol-all about one liter in size. The caps on some of the acids have deteriorated probably due to long neglect, and leakage was evident on some of the bottles. The inside of the cabinet was also rusted.

The HSEO emergency response team was called in to help dispose of the chemicals. Wearing chemical protective clothing, face shields, and respirators, HSEO officers first prepared spill control equipment in the area in order to contain any accidental spills. They then removed the organic chemicals from the cabinet. After that, they slowly poured the concentrated acids, one by one, into chemical waste containers already half full of water. The empty bottles were then rinsed and disposed of separately.

It turned out that these chemicals were left by a past graduate student who had already graduated and left the University.

Lessons learned and recommendations

• Chemicals can be dangerous. They must be properly stored in designated chemical storage areas.
• Incompatible chemicals must be stored separately to prevent accidental contact. The list of chemicals in this case actually includes all the ingredients needed for making high explosives and rocket fuels. Imagine what could happen if they actually come in contact.
• Periodic checks and proper documentation on chemical inventories are requirements for every lab. Try to minimize the amount of chemicals purchased. Disposing of surplus or unwanted chemicals can be very complicated and costly.
• Lab workers should be required to clean up reagents that they use after each project, or before they leave the department/university.

​

A postgraduate student in a local university prepared 450 mL of an electro-polishing solution by mixing concentrated nitric acid and ethanol in a 1:2 ratio as indicated in a published research paper. The student observed "no significant temperature rise" over 3 hours, he then capped the Winchester bottle and went home. About 4 hours later, the bottle exploded, scattering glass fragments to a distance of 12 meters and with enough force to break another Winchester bottle containing oil 1.75 meters away, and a plastic shield 4 meters away. Fortunately there was no one in the laboratory at the time, otherwise the powerful explosion could have caused serious injuries.

According to Bretherick's Handbook of Reactive Chemical Hazards, such mixture is "best described as an unstable... rocket fuel mixture"! In a correspondence between the safety personnel of the tertiary institute . and the author of this well-known reference, Mr Bretherick further commented that:

 

• It is important for any description of experimental conditions to specify whether the proportions are by weight or volume, the strength of the acid, and the grade of alcohol to be used. Different grades of ethanol can contain up to 5% or more of denaturants, of which some (methanol or isopropanol) could adversely affect the reactivity of ethanol and nitric acid.

• It has been known for 50 years that mixtures of ethanol with above 1 0% by weight of concentrated nitric acid are unstable, and that mixtures above 5% wt concentration should not be stored in closed containers, particularly after use as metal etchants, when the dissolved metal may catalyze the decomposition. It has also become clear during that period that nitric acid is the common reagent most often involved in violent chemical reactions, decompositions or explosions. This is a consequence of the tact that nitric acid, unlike other oxidants, still functions as such when cold and dilute, and oxidation is always accompanied by gas evolution, sometimes very slow but progressive. It is also able to form explosive ethyl nitrate by slow acid catalyzed esteritication.

• While mixtures of alcohols with perchloric acid (such mixtures are also used for electro-polishing) are largely free of these gas generation problems, they have their own potential problems. Perchloric acid is an excellent catalyst for esterification reactions. So its mixtures with alcohols will develop explosive alkyl perchlorates. Ethanol denatured with methanol would give both ethyl and methyl Perchlorate, the latter being less stable. Through long standing of the open mixture significant evaporation might occur and a dangerous concentration of Perchlorate might arise.

• It is important to establish whether etching solutions should be retained after use, where heavy metals (particularly catalyticallyactive transition metals) may have been dissolved. There are two distinct reasons forthis, the first being that such metals mayadversely affect the stability of the contaminated solution by accelerating the decomposition rate. Secondly, explosive fulminate salts of heavy metals could form in and separate from the used etching solution. Disposal of the used solutions, either from nitric acid or perchloric acid-based solutions should be considered an integral part of the whole operation.

These are valuable reminders for all material scientists who may need to use such etchant solutions, and in fact for all other researchers who use nitric acid for various purposes.

(This article first appeared on the June,1996 issue of SafetyWise)

 

The HKUST has recently contracted with Phoenix Controls to upgrade certain fume cupboards [fume hoods] to an energy saving mode.  By the use of motion sensors to detect active use of the fume cupboard, the upgraded systems will automatically reduce the flow of air when no user is present.  This upgrade will naturally raise questions about safety under the reduced flow condition.  The following discussion is to clarify the continued safe status of the modified fume cupboards.

The primary method of contaminant control within the laboratory is exhaust ventilation and, in particular, laboratory hoods.  Laboratory hoods are normally purchased from manufacturers who specialize in the design and construction of such equipment laboratory hoods.  The most important aspect of the hood is the aerodynamic entry characteristics.  For the hood to adequately control contaminants, the entry must be smooth.  This usually is achieved with an airfoil still at the leading edge of the workbench.  Often, beveled jambs at the side wall entry will improve the air flow.

In many cases, good performance of the fume cupboard correlates with a uniform face velocity.  For typical operation of laboratory hood, the worker stands at the face of the hood and manipulates the apparatus in the hood.  The indraft at the hood face creates eddy currents around the worker’s body and up to the breathing zone.  The higher the face velocity, the greater the eddy currents.  For this reason, higher face velocities do not result in greater protection as might be supposed.

Room air currents have a large effect on the performance of the hood.  Thus, the design of the room air supply distribution system is as important in securing good hood performance as is the face velocity of the hood.  The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) research project RP-70 results, reported by Caplan and Kuntson1, conclude in part:

- Lower breathing zone concentration can be attained at 50 cfm/ft2  face velocities with good air supply distribution than at 150 cfm/ft2 with poor air distribution.  With a good air supply system and tracer gas released at 8 liters per minute (1pm) inside the hood, breathing zone concentrations can be kept below 0.1 ppm and usually below 0.05 ppm.

For the reasons described above, an increased hood face velocity may be self-defeating because the increased air volume handled through the room makes the low-velocity distribution of supply air more difficult.  The interaction of supply air distribution and hood face velocity makes any blanket specification of hood face velocity inappropriate.  Higher hood face velocities will be wasteful of energy and may provide no better or even poorer worker protection.  Any well-designed airfoil hood, properly balanced, can achieve 0.10 ppm control level when the supply air distribution is good.  The bottomline:  SEPO and EMO will monitor to ensure that the ongoing modification work will not compromise personnel protection while achieving energy savings. 

​

1 K. J. Kaplan and G. W. Knutson, “Influence of Room Air Supply on Laboratory Hoods,” Am. Ind, Hyg. Assoc. J. 43(10):738-746(1982).