Pollution Prev. for Industrial Painters and Auto Body Repair

Published by:
Metro-Dade County
Department of Environmental Resources Management
33 S.W. 2nd Avenue
Miami, FL 33130-1540

Last Revision: June 1995

This document is published to help educate businesses on some of the environmental issues affecting them. It suggests options that may help businesses to operate in an environmentally appropriate manner. They are based on experience and simple common sense ideas. Many of the options go beyond what is required to remain in compliance with the regulations. Please refer to Chapter 24 of the Metropolitan Dade County Code ("Metropolitan Dade County Environmental Protection Ordinance") for the exact regulations.

What is pollution prevention?

It is the reduction or elimination of pollutants or wastes at the source. The idea behind pollution prevention is to avoid producing the waste in the first place. If the waste is not produced, then you don't have to worry about storage or disposal problems. Having less waste means a better environment for all of us.

What's in it for you?

Painters deal with many hazardous chemicals. Hey, it's part of the business! But, you can reduce the amount of waste your shop produces by following some simple pollution prevention tips. Look at some of the benefits:

* Save money * Protect workers, the public, and the environment! * Improve your company image! * Reduce the risk of liability!

What can you do?

Dade County D.E.R.M. (Department of Environmental Resources Management) is encouraging every business to reduce pollution by starting a waste reduction program. Here are some things to consider when setting up your program.

* Make a commitment to pollution prevention. This commitment should start at the top, with the owner or manager of your shop. It should be made a part of your company's policy.

* Employee participation. Every employee must be aware of the importance of waste reduction through pollution prevention practices. Their participation and suggestions in your waste reduction program will help to make it a success.

* Evaluate your shop's waste. Look around your shop to see how much and what kind of waste is being produced. This will make it easier for you to spot areas where pollution prevention tips can be applied.

* Find some new ideas. Talk to other employees, or vendors, or even inspectors. Maybe they can help you. Or look through trade journals or magazines. There is always a better way to do things.

* Make the change! Don't be afraid to experiment.

Many pollution prevention practices are low-cost and low-risk alternatives to help minimize waste and the resulting disposal costs. Most of the approaches are based on common sense and do not require sophisticated technology. This booklet contains some ideas to get you started. Your shop may already be using pollution prevention practices without realizing it!

Keep it clean!

Poor housekeeping results in spills and overflows. This may double your expense by making you pay to replace lost material and also for its treatment and disposal. It can also lead to accidents and worker injury. Good housekeeping is one of the easiest and least expensive way to reduce waste. Here are some tips:

* Keep your shop clean and your floors dry. Sweep floors and use dry or damp clean-up techniques. For example, use absorbent material for spills and if necessary, use a very small volume of water for final cleanup. This material should then be disposed of properly.

* Practice good inventory control. Mark the purchase date on containers and adopt a "first in, first out" policy, so that older materials are used up before new ones are bought.

* Keep all containers closed and properly labeled.

* Keep storage and work areas clean and well organized.

* Do not mix hazardous chemicals with non-hazardous chemicals. Otherwise all of the waste will have to be treated as a hazardous waste. This can be very expensive.

There are many different chemicals, machines, and processes used by painters. Often things are done a certain way simply because, "It's always been done that way." Just because it works does not mean that it is the best way. There is always room for improvement, and remember, "An ounce of [pollution] prevention is better than a pound of cure."

Why reduce "VOC" and increase Transfer Efficiency?

In case you were wondering, VOCs are Volatile Organic

Compounds. VOCs are often used as solvents in paints and for paint clean-up. Maybe you'll recognize some of these examples of VOCs: methyl ethyl ketone, methyl isobutyl ketone, toluene, or xylene. As the paint is applied to the surface, the solvents evaporate leaving behind the resins, pigments, and other additives. That's right they just disappear! Well, not quite...

They evaporate into the atmosphere where they may contribute to global warming, and react to create low-level ozone and smog. These pollutants have been shown to cause serious health and environmental damage.

1) Title I of the Clean Air Act Amendments of 1990 addressed this concern and led to the establishment of Reasonably Available Control Technology (R.A.C.T.) for some 18 source categories of VOCs. Some of the source categories that may affect painting operations include:

* Metal coating
* Furniture manufacturing
* Aerospace
* Plastic coating
* Ship building
* Architectural

Some typical methods that can be used to meet the R.A.C.T. requirements include:

* Use of low-solvent paint formulations (less than 3 lbs/gal of VOCs).

* Reduction in production hours.

* Use of incineration control equipment.

2) Title III of the Clean Air Act Amendments of 1990 lists 189 chemicals as Hazardous Air Pollutants (HAPs). Regulations are currently being developed establishing Maximum Achievable Control Technology (M.A.C.T.) standards for these HAPs. Facilities will be required to lower their air emission levels to those levels set forth in the M.A.C.T. standards. This is often the top 10% or better of control technology available. All of the applications, for each one of those chemicals, must be reviewed prior to promulgation of the standards. Guess what? Many of those chemicals found on the HAPs list are in paints and solvents. Some of these chemicals include:

* Methyl ethyl ketone, methyl isobutyl ketone, xylenes, toluene, methylene chloride, glycol ethers, etc. (For a complete list please contact the D.E.R.M. Air Section.)

As these new requirements are established, many companies may realize that it is more economical to change paint formulations and application methods, rather than installing costly control equipment.

TRANSFER EFFICIENCY is a measure of how much paint actually coats a surface compared to how much is applied. In spray painting, what doesn't coat the surface is usually called overspray. This overspray is a waste and can be expensive! As a result of increasing transfer efficiency:

* Less paint has to be bought.
* Air filters need to be changed less frequently.
* Paint booth cleanup is easier and less frequent.
* Less VOCs or HAPs are emitted when painting the same parts.

Transfer efficiency is determined by a number of factors. These can include:

* painting equipment.
* operator training.
* parts' hanging and racking configurations.


Low VOC Content Paint'
Conventional paints can contain from 60-80% VOCs or higher. The VOCs (or solvents) are used as a carrier to help the paint flow smoothly and spread evenly across the surface to be coated. The rest of the paint is generally called "solids." It is the quantity of solids in a paint that will determine its covering ability. There are six general types of low VOC content paints. (See Pg. 6)

1) High Solids- These paints have more solids and less solvents. Unfortunately, as you remove the solvents the paint becomes very thick or viscous, and does not flow very well. For you chemists out there, what they do to compensate is use shorter resin molecules, but give them more cross-linking sites.

NOTE: For calculating total VOCs released when using high solids paints, the manufacturer's proportion of ingredients may not be enough. Because the resin molecules are shorter, during baking some of them may be released as VOCs themselves.

2) Waterborne- In water-borne (water-based) paints, water has been substituted as a carrier to replace most of the VOCs. Performance properties have greatly improved, and are comparable with most conventional paints. They will cure in ambient conditions, over a somewhat longer period of time.

NOTE: Waterborne coatings still contain a small amount of VOCs. The question is how much and what type.

3) Multi-component- These are generally two-part epoxy or urethane paints. Individually each part can be stored for extended periods of time. The VOC content and viscosity are generally low. However, once the components are mixed, the (irreversible) curing process has begun. The useful potlife can range from minutes to hours. The mixing equipment and application equipment can be separate units or combined into a single unit. For example, mixing can occur at the gun tip. This allows the recovery and reuse of the individual components in the lines.

NOTE: Two-part urethanes usually use isocyanates, which may lead to respiratory problems with prolonged exposure.

COMPARISON OF LOW VOC CONTENT PAINT FORMULATIONS

Type; V.O.C. content[1]; Viscosity; Cure; Performance; Appearance; Coverage Rate
Low Solids (Conventional); 60-80%; Low; Ambient/Bake; Average- Good; Good-Very Good; Low
High Solids; 20-40%; Medium; Bake; Good; Average; Medium
Waterborne; ,1%-20% (<5%-30%)[2]; Low; Ambient/Bake; Average; Average-Good; Low
Multi-component; <1%; Low; Ambient; Very Good[3]; Good[3]; High
Radiation cured; <1%-5%; Low; Ambient (UV or E.B.); Good; Good; High
Powder Coating; <1%; -----; Bake; Very Good; Good; High
100% solids liquid; <1%; High; Bake; ?; Average; High

[1]Values quoted for VOC content are approximations that are based on a variety of reference data. In general, an error of + or -5% should be assumed. Individual formulation may have properties very different from those indicated.
[2]() Value indicates VOC content based on formulation less any water.
[3]Epoxies will chalk on the surface in sunlight, but this generally does not affect their performance properties. [end of table]

4) Radiation cured -These paint are. generally of two types: Ultraviolet (UV) cured and Electron Beam (E.B.) cured. The difference between the two is mainly equipment costs and production rates. Generally these paints have very low VOC content, and curing is performed through a photochemical reaction. Curing occurs rapidly when any coated surface is exposed to the suitable radiation. This means high production rates are possible, but blind holes are difficult to cure.

5) Powder coating-These are 100% solids coatings. They have no VOCs as carriers, and appear as a powder. The part is preheated and/or the paint particles are electrostatically charged. These particles then "cling" to the surface. They must then be cured by baking. They are limited to fairly thick coatings (10 mil or greater), but generally provide very good performance properties. They allow an extremely efficient operation since up to 99% of any overspray can be collected and reused directly. Less than 1% is lost to particles eventually grinding into a fine dust.

6) 100% solids (not powder) - This is one of the newest innovations and like powder coatings these are also 100% solids. However, the resin itself appears as a liquid rather than a solid. This coating is fairly viscous, and usually requires modification of application equipment. It is so new that performance properties are still being evaluated, but it has already proven suitable for decorative coatings.

Things to think about ...

Ambient Cure- Low VOC paints are generally more sensitive to temperature and humidify conditions

Coverage Bate- Low VOC paints generally have greater coverage rates. This can mean higher production rates, but also a painter will have to move faster to prevent excessive film build.

Viscosity- Higher viscosity may require the modification of application equipment. Heating is a simple way to reduce viscosity for application purposes. Solvents should not be used to thin these paints to a desired viscosity.

Painting application equipment

Below are some of the methods for applying paint. Changing application equipment can increase transfer efficiency. (See Pg. 9)

NON-ATOMIZING APPLICATION:

Brush & Roller-Paint is applied by a brush or a roller.

Dip - The part is immersed into a tank of the paint. Film thickness is controlled by the viscosity.

Flow- From 10 to 80 separate streams of paint are directed to coat all surfaces of the part as it passes. Film thickness is controlled by the viscosity.

Curtain- A curtain, or waterfall flow, of paint coats a part conveyed horizontally. The paint flow rate (and thus film thickness) can be controlled by varying the slot opening. This is often used for coating sheet metal, or similar goods.

Electrodeposition (E-Coat)- The paint is electrically deposited on the surface of the part from a waterborne organic solution containing the ionized resins.

AIR SPRAY GUNS:

Low-Volume High Pressure (Conventional)- Compressed air is used to atomize the paint. Air pressure can range from 40-80 psi, with An air volume flow rate of about 3-25 cfm.

High-Volume Low-Pressure (H.V.L.P.)- Compressed air is used to atomize the paint, but at a much lower air pressure (10 psi or less) and with a much higher air flow rate than conventional paint guns.

1) Turbine type - A high volume of air is supplied to the gun at a low pressure. Often up to four guns may be run from a single turbine. Also the air output can be heated. This heating can be used to lower the viscosity of some paints (e.g. high solids). The main disadvantage is that the air hose is larger and a bit cumbersome.

2) Compressor & pressure reducer - An air compressor provides the air that is reduced in pressure, usually at the gun itself. The hose size is comparable to conventional guns. However, a separate air heater would be necessary if heated air was desired to lower paint viscosity.

TABLE [refer to source document]

PROPERTIES OF VARIOUS PAINT APPLICATION METHODS

Method; Transfer Efficiency[1]: Flat, Table leg, Wire cage; Finish Quality; Coating Rate; Uniform Thickness; Recessed Areas; Internal Corners; Electrostatics; Costs

NON-ATOMIZING APPLICATION

Brush & Roller; >96; >96; >96; Poor; Low; Poor; Poor; Average; No; Low

Dip; >98; >98; >98; Average; High; Average; Varies; Varies; No; Low

Flow; >98; >98; >98; Average; High; Average; Varies; Varies; No; Low

Curtain; >98; >98; >98; Average; High; Average; Varies; Varies; No; Low

Electrodeposition (E-Coat); >98; >98; >98; Good; Low-High; Very Good; Good; Good; No; High

AIR SPRAY

Low-Volume High-Pressure (Conventional); <25; <15; <10; Very Good; Low-High; Average; Average; Poor; Operational; Low High-Volume Low-Pressure ((H.V.L.P.); <55; <25; <20; Good; Low- Medium; Average; Average; Average; Optional; Low Either w/electrostatics[2]; +20%; +40%; +45%; Same; Same; Better; Lower; Lower; -----; Higher

AIRLESS (HIGH PRESSURE) SPRAY

Airless; <55; <35; <30; Average; Medium-High; Average; Average; Good; Operational; Medium

Air-assisted airless; <55; <35; <30; Average; Medium-High; Average; Average; Good; Operational; Medium

Either w/electrostatics[2]; +5%; +40%; +40%; Same; Same; Better; Lower; Lower; -----; Higher

ROTARY ATOMIZERS

Disc[2]; <85; <80; <80; Very Good; Low-High; Good; Poor; Poor; Yes; High

Bell[3]; <95; <85; <85; Very Good; Low-High; Good; Poor; Poor; Yes; High

POWDER COAT

Powder Coat; <95; <95; <95; Good; Low-High; Good; Poor; Average; Optional; High

[1] Values quoted for transfer efficiency are approximations that are based on a variety of reference data. In general, an error of + or - 5% should be assumed. Individual pieces of equipment and operations may perform much better or much worse than these figures. Values quoted with the "<" (less than) symbol reflect that poor operator technique, racking, and equipment maintenance and set up, can reduce these transfer efficiency ratings.

[2] Values indicate the change in properties when electrostatics are combined with the equipment. Transfer efficiencies are to be added to the values above.

[3] The values quoted for rotary atomizers assume the use of electrostatic systems. [end of table]

AIRLESS (HIGH PRESSURE) SPRAY

Airless- Paint is atomized by increasing it's pressure into the range of 500-6,500 psi. There is no pressurized air used. High viscosity fluids can be applied with this method. The gun is generally easier to maneuver since there is only one hose attached. However, there is a serious risk of injury from paint being injected under the skin. Nozzles are expensive, and increased maintenance is required. This is often used where very high coating rates are desirable.

Air Assisted Airless- Similar to the standard airless, the fluid delivery pressure is reduced to 150 to 800 psi and an air pressure of 5 to 30 psi is used. This air is used for shaping of the spray pattern.

ROTARY ATOMIZERS:

Disc- Paint is delivered to the center of a disc that is spinning at very high speeds. From there the paint is carried by centrifugal forces to the edge of the disc and released. The paint is very finely atomized in the process Paint then travels in all directions tangential to the disc and must be attracted to the part using electrostatic forces.

High viscosity fluids can be applied with this method. Rotational speeds can vary from 1,000 to 10,000 rpm for low-speed (larger disc size) units, and from 10,000 to 60,000 rpm for high speed (smaller disc size) units.

Bell- Similar to a disc, the edges of the disc have been curled up to face a specific direction. This provides a more directed paint delivery.

POWDER COATING:

Fluidized Bed- The powdered paint is agitated into a "suspension" by forced air from the bottom of a container. Parts are then immersed in the bed where they are coated.

Powder Spray- The powder is sprayed inside an enclosed booth. Any overspray can be vacuumed up and reused.

Powder Slurry Spray- The powder is mixed with water to form a slurry. This slurry is then sprayed with conventional equipment. Preheating or electrostatics are not needed.

(See "Low VOC Content Paints--Powder Coating" on Page 6).

Electrostatics

When electrostatics are used, the atomized paint droplets are charged at the tip of the gun by a charged electrode. The part to be painted is electrically neutral, and the charged paint droplets are thus attracted to it.

Proper Grounding- The part to be painted must be conductive and properly grounded. It is important that any paint hooks used are properly cleaned and conductive. This means that in a conveyor operation, the conveyor, conveyor wheels, conveyor beam and the buildings steel frame must all be conductively connected and grounded. The negative side of the power supply is connected to the gun, and the positive side is properly grounded, thus completing the circuit.

For maximum efficiency, the part to be coated should be the closest grounded object to the tip of the gun. If the "circuit" is in any way insulated or poorly connected, ungrounded objects (including employees) in the vicinity may build up a charge that dissipates by arcing when a grounded object is brought near. This can lead to fires or explosions and resulting injuries. Square or simile hangers with sharp edges can help to cut through any pain build-up when hanging parts.

Wraparound Effect- Paint particles that would normally travel past the part may in fact be attracted to the part and coat the edges and some of the back side of a part. This may or may not be beneficial.

Faraday Cage Effects- Because charged paint particles will always travel towards the nearest ground, they are preferentially attracted towards external edges or corners, or the tops of recess, rather than into internal edges or corners, or similar recessed areas. Fine tuning of the amount of charge used, as well as manual touch-up with non-electrostatic equipment may be required.

Hanging or Racking

Hanging and racking parts properly can have a significant impact on production rates and transfer efficiency in painting operations. Generally parts should be hung and racked to optimize line density and minimize overspray at the edges from being wasted. Instead of using single hooks, investigate using racks that can hold multiple parts.

* Racking is useful for small parts that can be preloaded onto racks. The racks can then be loaded on to the line.

* Increasing line density also allows decreasing line speed to allow more time for better cleaning and curing.

Operator technique

* Keep guns and other equipment clean and well maintained.

* Use the minimum amount of paint fluid pressure to meet the production rate.

* Use the minimum amount of air pressure for correct atomization. If the air pressure is set too high, too fine of an atomization can occur. Paint droplets may actually dry before they reach the surface, resulting in "dusting" of the surface. If the air pressure is set too low, not enough atomization occurs leading to drips, runs, and sagging.

* Keep guns perpendicular to the surface to be coated as much as possible. Avoid sweeping arcs with the arm or wrist.

* Keep guns at a uniform distance from the surface. (6-8" for air spray guns.)

* Move the gun at a uniform speed.

* Overlap each stroke by the same amount.

* The gun should be moving prior to triggering.

* Guns should be triggered at the beginning and end of each stroke.

* Exterior edges should be sprayed first.

Sprayed paint should not be directed straight into internal corners but rather each side of the corner should be sprayed.

Spray Booths & Filters

A spray booth is an enclosed area equipped to capture overspray paint and replace the exhausted air with fresh make-up air.

* Baffle type filters can take heavy loading levels, but aren't as good at removing smaller particulates.

* Strainer type filters are good at removing smaller particulates, but tend to load up quickly.

* Combinations of a baffle type filter followed by a strainer type filter can offer the benefits of both.

* Filters should be replaced regularly. Filters that are loaded or clogged reduce the air flow, increase the work of fans, consume more energy, and may lead to leaks through cracks and around the edges of filters.

* Filters may be disposed in the trash if they are completely dried and the paints captured contain no heavy metals.

* Under no circumstances should solvents from gun cleaning be sprayed directly into filters. These solvents should be properly collected and recycled or disposed.

* Fresh make-up air should be filtered to minimize dust entering the booth during painting operations.

* The flow of air through the booth should be as linear as possible, usually in the same direction that paint is being sprayed.

* Excessively high air velocities through the booth will actually increase overspray and reduce transfer efficiency.

* Operators need a clean supply of air. This can be from supplied air lines, or from using air purifying respirators (APRs). Filters in these APRs should be replaced regularly. Common dust masks do not provide filtration of dangerous VOCs and should not be used alone. These chemicals have been shown to cause serious health problems.

* The table below lists some of the performance criteria that are required for spray paint booths

TABLE

SPRAY BOOTH DESIGN CRITERIA (for booths with disposable paint arresting filters)

Air velocity; 100 feet per minute at work location

Net filter area:

Auto; Not less than 40% of the vertical cross-sectional area of the booth.

All others; Not less than 75% of the vertical cross-sectional area of the booth

Fan static pressure; 1/2 in w.g. (water gauge) at capacity to meet required air velocity.

Fan design; Duct type with non-sparking blade material, enclosed belt housing, as required by local Fire Department regulations.

Discharge position; Discharge stack must terminate in a vent up position to the atmosphere with minimum height of three feet (3') above the highest roof line within a twenty-five foot (25') radius.

Stack head/raincap; Stack head/raincap may be of the hinged-up blast damper type (through the roof) with weep through the building. Use of conical type raincaps as well as water pans is prohibited.

All booths must meet Building and Fire Department regulations. Prior to installation and operation of the spray booth, plans must be submitted, along with an air permit application for review to the D.E.R.M. Air Section. [end of table]

Gun & line Cleaning

A variety of solvents are often used for gun and line cleaning. Here are a few easy steps to minimize solvent usage and the resulting wastes that are produced:

* Use a single solvent. If possible choose a solvent that can be used to thin the paint as well.

* Use shorter lines.

* Plan painting schedule to reduce the need for frequent color changes. If possible, schedule from lighter to darker colors.

* Run compressed air through the lines prior to cleaning. This can force out any excess paint, that can then be reused.

* Use waterborne (water-based) paints in order to minimize the need for cleaning with solvents.

* A recirculating filter system can be used for solvents from gun and line cleaning.

* Use a solvent distillation unit to recover spent solvents for reuse over and over again. Still bottoms must be disposed of properly, usually as a hazardous waste.

Auto Body Repair & Refinishing

Auto body shops can save money by following many of the other tips in this booklet. Here are some tips especially for these shops:

* Priming a vehicle is considered painting, and must be performed inside a spray booth.

* Use dry clean-up techniques such as sweeping and vacuuming for the booth.

* Water from a washing or wetting of the spray booth must be collected and disposed of properly. Discharge directly to ground through drain holes in the booth is not permitted.

* Under no circumstances should solvents from gun cleaning be sprayed directly into filters. These solvents should be properly collected and recycled or disposed by an approved hauler.

Hazardous materials storage

Below are some suggestions for storage of hazardous materials:

* Store on an impervious (sealed) surface, i.e. resists infiltration or corrosion by the stored materials.

* Store under cover, whether indoors or outdoors, to keep out the rain. Check with Fire Department.

* Provide some type of secondary containment that will hold up to 110% of the largest container stored in the area. This area should be able to catch and contain any leaks or spills.

* Label waste containers properly, including contents and date of generation for any hazardous wastes.

* Make sure drums are easily accessible but not stored in high traffic areas where they can be easily knocked over.

* Be sure containers are properly sealed. Regularly check for any signs of leak, rust, etc.

What to do with hazardous waste?

* Keep all records of Hazardous Waste handled on site for at least three (3) years. This includes amounts purchased, stored, reused, and hauled away.

* Hazardous waste should be shipped out by an properly permitted hauler to an EPA approved treatment, storage, and disposal facility. Check for all the proper local, state, and federal licenses. (Contact D.E.R.M. for a list of approved haulers.)

The facility generating the waste should obtain an EPA identification number from the address below, unless officially classified as a "Conditionally Exempt Small Quantity Generator."

Bureau of Waste Planning and Regulation
Twin Towers Office Bldg
2600 Blair Stone Road
Tallahassee, FL 32399-2400
Ph: (904)487-3299

Phone Numbers

METRO-DADE COUNTY

Dept. of Environmental Resources Management

Main Switchboard (305) 372-6789
Wastewater Section (305) 372-6500
Air Section (305) 372-6925
Hazardous Facilities Section (305) 372-6600
Liquid Waste Transporters (305) 372-6804

FLORIDA DEPT. OF ENVIRONMENTAL PROTECTION

Southeast Region Office (407) 433-2650
Tallahassee Office (904) 488-0300

For more information ask for "Florida's Handbook for Small Quantity Generators of Hazardous Waste"

Sources of Additional Help for Pollution Prevention

Metro-Dade County

Department of Environmental Resources Management

Pollution Prevention (P2) Program (305)372-6789. The P2 program publishes a quarterly newsletter, has a library of information, holds workshops and training periodically, and provides on-site consultation to select facilities.

Florida Department of Environmental Protection

Pollution Prevention Program (904)488-0300. This program provides technical assistance in the form of informational resources, research for waste reduction options, telephone consultation, experts and speakers for workshops, and on-site waste reduction assessments to business, industry, and governmental agencies in Florida.

The Florida Clean Air Act

Small Business Assistance Program

1-800-722-7457. This office assists small businesses with compliance under the new Clean Air Act Amendments.

Waste Reduction Resource Center

1-800-476-8686. The center provides information to persons in EPA's Region IV (Florida included). Their library contains over 3000 journal articles, case studies, technical assistance reports and books.

DERM
Department of Environmental Resource Management
Office of Sustainable Environment & Education
Pollution Prevention Program
33 S.W. 2nd Avenue
Miami, Florida 33130-1540

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Last Updated: April 21, 1997