# Degreasing with TCE in Commercial Facilities: Protecting Workers

Background Document

## Prepared by Eastern Research Group, Inc. (ERG)

This preliminary document is being presented at the TCE Expert Public Workshop. Our goals for the workshop are to:

• Identify and understand the criteria that alternatives (chemical and/or no chemical) will need to satisfy to be

an effective replacement.

• Understand lessons learned from previous work that can be used to inform future substitutions.

• Identify a list of measures, for example, for worker protection, other than chemical substitution, that could be

used to reduce exposure to TCE in the given applications. Our goals for presenting this preliminary document are to provide a starting point for discussions of worker protection and risk management for these uses of TCE. This preliminary document presents current examples of best practices; we are interested in your thoughts and feedback on the information in this document, the way it is presented, whether it meets our goals, and how it can be more effective at reducing exposure to TCE.

### Background Document | 1 

# T he 

# I ssue 

# & H ow t o 

# U se 

# T h i s 

# D ocumen t


## What is TCE? TRICHLOROETHYLENE (also known as TCE or by its proper chemical name, 1,1,2-trichloroethene) is a chemical that is commonly used as a solvent. As a liquid, TCE is highly volatile, meaning that it quickly produces vapors. TCE has a pleasant, sweet smell, though you can breathe it in without smelling it. TCE vapors can also be absorbed through your skin. Single (acute) or short-term exposure to high concentrations of TCE vapors can irritate the respiratory system and skin and induce central nervous system effects such as light-headedness, drowsiness, and headaches. Changes in heart beat have also been reported following TCE exposure. In extreme circumstances, overexposure can lead to unconsciousness and even death (ATSDR, 1997). Repeated (chronic) or prolonged exposure to TCE has been associated with effects in the liver, kidneys, immune system, central nervous system, reproductive system and developmental effects in the developing fetus. TCE is carcinogenic to humans by all routes of exposure. TCE that enters your body can be transferred to your fetus if you are pregnant or to your child while you are nursing (EPA, 2011). 

## How to Use This Document Degreasing is the process of using solvents to remove grease, fats, oils, waxes, or soils from surfaces. The surfaces being cleaned typically are made of metal, but can also be glass or plastic. EPA prepared this document to help commercial facilities that perform degreasing as part of their operations to reduce their health risks to TCE. You may find this document helpful if you perform degreasing with TCE in any of the following commercial settings:

• Repair shops —shops that repair automobiles, motorcycles, bicycles, or electronics.

• Fabrication shops — shops that fabricate metal, glass, or plastic components into a final product.

These include a wide range of large and small facilities that produce automobiles, aircraft, appliances, motor vehicle parts, machine parts, and jewelry.

• Metal plating shops —shops that plate, or coat, metal onto a surface.

• Electronics assembly shops —shops that assemble a wide variety of electronic devices onto circuit

boards, such as electric capacitors, semiconductors, and electronic instrumentation. Degreasing is performed in a wide variety of facilities, both large and small. The methods used to degrease parts depend heavily on a facility’s exact function. If you do not see your exact facility type here, you may still be able to use this document. If you know the type of degreasing you perform in your shop, you can refer to the sections that discuss that type of degreasing. Table 1 identifies the type of degreasing typically performed in each of the commercial settings discussed in this document.

### Background Document | 2 

## Outline Personal Protective Equipment When Using TCE

.......................................................................................... 3 Skin Protection

............................................................................................................................... .......................................... 3 Eye Protection

............................................................................................................................... ........................................... 3 Respiratory Protection

............................................................................................................................... ........................... 4 

### Repair Shops

............................................................................................................................... ................................... 5 Technologies That Eliminate or Reduce Risks from TCE

........................................................................................ 6 Protecting Workers from TCE

............................................................................................................................... ............. 8 Workplace Practices

............................................................................................................................... ............................. 10 

### Fabrication Shops

............................................................................................................................... ........................ 12 Technologies That Eliminate or Reduce Risks from TCE

....................................................................................... 13 Protecting Workers from TCE

............................................................................................................................... ............ 15 Workplace Practices

............................................................................................................................... .............................. 17 

### Metal Plating Shops

............................................................................................................................... .................... 18 Technologies That Eliminate or Reduce Risks from TCE

....................................................................................... 19 Protecting Workers from TCE

............................................................................................................................... ............ 21 Workplace Practices

............................................................................................................................... ............................. 23 

### Electronics Assembly Shops

............................................................................................................................... . 24 Technologies That Eliminate or Reduce Risks from TCE

...................................................................................... 25 Protecting Workers from TCE

............................................................................................................................... ........... 28 Workplace Practices

............................................................................................................................... ............................. 29 

### References

............................................................................................................................... ...................................... 31 T

able 

### 1.D egreasing 

### M e t ho d s 

### C o mm only 

### U se d a t 

### S hops


## Type of Shop Degreasing Method Spot Cleaning Cold Cleaning Vapor Degreasing Repair shops X X X Fabrication shops X X Metal plating shops X X Electronics assembly shops X X

### Background Document | 3 IF YOU USE TCE

- based degreasers, you should always wear proper personal protective equipment (PPE). Effective types of PPE are described below. 

## Skin Protection TCE can absorb through your skin, which can potentially be hazardous (NJDH, 2008) . Solvent-resistant gloves that can be effective against TCE include (NJDH, 2008):*

• Silver Shield®/4H® gloves

• Viton® fluoroelastomer gloves

• Barrier® model gloves Gloves cannot permanently protect you from exposure to solvents. It is important to remove and replace your gloves when they become wet with TCE. Wear long sleeves to protect your skin. Coveralls can provide good skin protection for most of your body. Coveralls resemble jumpsuits and cover your torso, legs, and arms, and can even have attached hoods. Coverall brands that can effectively protect against TCE include (NJDH, 2008):*

• Tychem® F, BR, LV, Responder®, and TK coveralls

• Zytron® 500 coveralls

• ONESuit® TEC coveralls

• Trellchem® HPS and VPS coveralls If you get TCE on your skin, immediately wash the contaminated area with water and soap. Provide a hand washing station, with soap or soap solution dispensers, near every cleaning or degreasing station. 

## Eye Protection Wear chemical splash goggles (Figure 1) when using TCE to protect your eyes against any splashes. Wearing a chemical splash face shield (Figure 2) over your goggles can provide extra protection for your face.

* Disclaimer of Endorsement: Reference herein to any specific commercial products, process, or service by trade name, trademark,

manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government. Figure 1. Chemical splash goggles. Figure 2. Chemical splash face shield.

### Background Document | 4 Eye wash stations (Figure 3) should be provided near cleaning or degreasing stations. If you get TCE in your eyes, rinse them in the eye wash station immediately for at least 15 minutes to limit the damage to your eyes. Make sure the station is unobstructed so a worker can get to it quickly. 

## Respiratory Protection If workers are overexposed to TCE vapors, and if you cannot use the methods discussed in the rest of this document to protect them, respirators may be needed. The most effective respirators for TCE are full-facepiece respirators with positive pressure supplied air or a self contained breathing apparatus (SCBA) (Figure 4). These types of respirators have an assigned protection factor (APF) of 10,000. This means workers using these types of respirators will inhale 10,000 times less TCE than workers wearing no respiratory protection at all (NIOSH, 2011). Note that dust masks (N95 respirators) (Figure 5) do not protect against TCE. 

# X

Figure 4: Full-facepiece respirator (with supplied air). Figure 5: N95 respirators do not protect against TCE. Figure 3. Eye wash station.

### Background Document | 5 REPAIR SHOPS take items such as automobiles, bicycles, or electronics apart to find and fix the cause of their malfunction. During repair, service item components are cleaned to remove anything that would compromise the item’s operation. The component may be cleaned in place or removed from the service item, then re-installed once cleaned. How technicians clean the components depends on what they are servicing. Repair shops most commonly use the following degreasing processes:

• Spot cleaning. The cleaner is sprayed directly onto components, or dabbed or soaked onto a rag that

is used to wipe components clean. Usually, the cleaning solvent is applied in excess and then allowed to air-dry. The components can be cleaned in place or removed from the service item for more thorough cleaning. This cleaning method may occur at any type of repair shop.

• Cold cleaning. Components are removed from the service item and are cleaned by spraying,

brushing, flushing, or immersion in a non-boiling (i.e., “cold”) solvent, as shown in Figure 6. They are then dried and reinstalled into the service item. This cleaning method is most often used at automotive repair shops.

• Vapor degreasing. Degreasing

solvents are boiled to produce a hot vapor (Figure 7). Components are suspended just above the bath, where the condensation of hot vapors cleans them. They are then reinstalled in the service item. This cleaning method is most often used at electronics repair shops. Receipt of Service Item Removal of Service Components Cleaning of Service Components S POT C LEANING

Cleaned Components Reinstallation of Cleaned Components C OLD C LEANING V APOR D EGREASING

Figure 6. Cold cleaning system used for cleaning components.

### Background Document | 6 

## Technologies That Eliminate or Reduce Risks from TCE Due to the variety of components and contaminants encountered at repair shops, it is difficult to identify specific alternatives that will work across all shops. Choosing the most suitable alternative will depend on the nature of the serviced components, their contaminants, and the needed level of cleaning. Further, the cleaning processes already in use at a given shop will determine what alternatives are available. To choose the most appropriate one, it is important to evaluate the current cleaning process first. This includes:

• The source of the contaminant. If the contamination occurs at the shop, consider changing the

process to eliminate its source. This would eliminate the need for cleaning components. For example, electronics repair shops can eliminate the need for cleaning by using a low-solids flux instead of a conventional rosin flux (as discussed below).

• The types of components that must be cleaned—specifically the materials of construction (carbon

steel, stainless steel, aluminum, etc.), type of surface (textured or smooth), and shape (simple or complex).

• The types of contaminants that must be removed (heavy oils, light oils, greases, waxes, dirt, salts,

etc.).

• The extent of cleaning needed. Determine the minimum cleanliness specifications for your

components. Make sure you do not apply more cleaner than is necessary. Once you have evaluated these factors for the shop’s cleaning method, work with vendors to determine which alternatives would best meet your cleaning needs. 

### Low-Solids Fluxes This alternative is specific to electronics repair shops. Low-solids fluxes are used in the same way as conventional fluxes. However, their residues dry rapidly, leaving behind little or no residues on the circuit boards; this eliminates the need for solvent cleaning. Figure 7. Vapor degreasing system used for cleaning components.

### Background Document | 7 The successful application of low-solids fluxes will depend on the specific needs of the component being serviced. For some components, even trace amounts of residues will compromise the reliability of repaired electronics (EPA, 1996); therefore, these fluxes should only be used in servicing electrical components that are less sensitive to any remaining flux residues. 

### Bake-Off Ovens This alternative is specific to automobile, motorcycle, or bicycle repair shops. Bake-off ovens can be used as an alternative to TCE degreasers. These ovens are designed to decompose dirt and grease, leaving behind a dry residue that can be brushed off. Bake-off ovens produce a smaller volume of waste compared to liquid cleaning alternatives (EPA, 1991). However, these systems can only be used on components that can withstand high heat. 

### Water-Based Cleaning This alternative, which applies to any type of shop, substitutes the use of solvents with water-based chemistries. The degree of substitution can range from completely eliminating solvents (i.e., aqueous cleaning) to partially eliminating solvents (i.e., semi-aqueous cleaning). Water-based cleaning solutions can include various cleaning ingredients such as acid or alkaline chemicals, detergents, water conditioners, corrosion inhibitors, and foam stabilizers (PPRC, 1996a). Components can be cleaned using the following methods:

• Manual cleaning , in which water-based cleaning solutions are sprayed or wiped onto components

and brushed clean.

• Hot soap washing , also known as hot tank washing, in which components are immersed in a

heated aqueous detergent. The system is automated and uses air and mechanical agitation to more thoroughly clean components.

• Spray cleaning , in which components are placed in an enclosed chamber and sprayed with the

cleaning solution using high-pressure jets (Figure 8).

• Ultrasonic cleaning, in which components are immersed in the cleaning solution and subjected to

high-frequency sound waves that form bubbles on the surface of the components (Figure 9). The bubbles create a mechanical cleaning action.

Figure 8. Spray cleaner that uses an enclosed chamber to prevent worker exposures to the cleaning solution.

### Background Document | 8 

### Closed-Loop Vapor Degreasers This alternative is specific to electronics repair shops. If substitution of TCE is not possible for vapor degreasing operations, consider installing a closed-loop vapor degreaser (Figure 10). This system cleans components in an air-tight chamber, which significantly reduces emissions and can also improve cleaning and product quality. Once the components are cleaned, vapors are exhausted to the outdoors before the chamber door can be opened. After the vapors are exhausted, workers can open the door and remove the cleaned components. Compared to conventional open-top vapor degreasers, closed-loop vapor degreasers can reduce vapor emissions by as much as 98 percent (NEWMOA, 2001).



## Protecting Workers from TCE In protecting your workers, you’ll use engineering controls—protective practices involving technologies and equipment. If it is not possible to eliminate the use of TCE from your cleaning operation, consider installing Figure 9. Ultrasonic cleaning tank.

Figure 10. Closed-loop vapor degreaser.

### Background Document | 9 engineering controls. The control options that apply to repair shops will depend on the type of degreasing system used at the shop. The control options listed below will protect workers either by:

• Limiting how much TCE gets released directly into the workplace before it comes into contact with

workers; or

• Limiting how much contact the workers have with TCE after it has been released into the workplace. Generally speaking, the first approach is most desirable, as it not only limits the potential for worker exposures but also the potential for releases into the environment. For spot cleaners, the engineering controls listed below focus primarily on limiting how much contact workers have with TCE after it has been applied to service item components. Because of the direct nature of spot cleaning, where TCE is sprayed or dabbed directly onto components, there are limited opportunities for introducing technologies or equipment that can reduce TCE releases into the workplace before it comes into contact with workers. For cold cleaners and vapor degreasers, the engineering controls listed below focus primarily on limiting how much TCE gets released directly into the workplace before it comes into contact with workers. Some options are available for limiting worker exposures to TCE after it is released into the workplace, but they are limited to the installation of exhaust systems. 

### Spot Cleaners

• Isolate cleaning activities—physically separate the cleaning station from the rest of the shop.

• Use ventilation to remove vapors from the cleaning station. There are two types:

— General mechanical ventilation involves the removal (exhaust) of dirty air and the supply of fresh

air within the building. In repair shops, it is often provided by the building’s heating, ventilation, and air conditioning (HVAC) system. The fresh, make-up air should enter on the opposite side of the room from the exhaust vents. It should be provided by outside air and not by air from other parts of the building. The exhaust air should exhaust to the outside of the building.

— Local exhaust ventilation provides exhaust ventilation close to the cleaning station. It captures

and removes TCE vapors at the source before they enter the air inside the shop. Local exhaust ventilation should exhaust to the outside and not to other parts of the shop. 

### Cold Cleaners

• For open cleaning tanks, install a vapor-tight cover to limit the escape of solvent vapors whenever

components are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Cover the solvent bath with a layer of water that is 2 to 4 inches thick. This water cover will float over

the solvent bath and limit the amount of TCE that evaporates out of the bath and into the workplace (EPA, 1981).

• If using spray equipment, consider using a solid-fluid stream sprayer. Spray pressures should not

exceed 10 pounds per square inch (psi) to avoid unnecessary misting of the cleaning solvent (KSUPPI, 2010). Avoid using atomizing or shower-type sprayers, which can generate more vapors.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit to reduce the amount of solvent

### Background Document | 10 that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace. 

### Vapor Degreasers

• For open-top degreasers, install a vapor-tight cover to limit the escape of solvent vapors when

components are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Install a condenser coolant thermostat switch. This switch will automatically shut off the heater

whenever the coolant temperature exceeds the maximum recommended by the equipment manufacturer.

• Install a solvent level control switch. This switch will automatically shut off the heater whenever the

liquid level drops below the minimum recommended by the equipment manufacturer.

• Install a vapor level control switch. This switch will automatically shut off the heater whenever the

vapor level rises above the maximum height recommended by the equipment manufacturer.

• Install a second set of cooling coils. Known as “freeboard chillers,” these coils prevent vapors from

escaping into the workplace. Note that freeboard chillers are not the same as the primary cooling coils that may already be installed in your vapor degreaser. The primary cooling coils are used to adjust the vapor height within the degreaser. They do not provide the same level of protection from vapors as freeboard chillers.

• For air-tight or air-less degreasing systems, install a differential pressure gauge. This gauge can be

used to verify that the system is not leaking.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace. 

## Workplace Practices If it is not possible to eliminate the use of TCE from your cleaning operation, consider implementing the following work practices and administrative controls: 

### Spot Cleaners

• Establish guidelines on when it is absolutely necessary to clean components with TCE; prohibit its use

otherwise.

• Encourage or require employees to brush or scrape dirty components to remove caked-on solids.

This will improve cleaning efficiency and reduce the amount of cleaner needed for spot cleaning. 

### Cold Cleaners and Vapor Degreasers

• Cold cleaning or vapor degreasing should never take place in the same room as soldering operations.

Soldering operations generate intense heat that can decompose the solvent vapors to produce phosgene, a gas that is even more toxic than TCE (NOHSC, 1989).

• Cold cleaners and vapor degreasers should be situated in large, open locations with good general

ventilation. These locations should be isolated from the rest of the shop.

• Cold cleaning and vapor degreasing equipment should only be used in accordance with the

equipment manufacturer’s specifications.

### Background Document | 11 • Vapor-tight covers should be closed at all times except during entry and removal of components.

• When the cover is open, avoid subjecting the tank to direct drafts, particularly from standing fans or

ventilation ducts. These drafts can carry TCE vapors into surrounding work areas.

• For cold cleaners, maintain a freeboard ratio of 75 percent or more. For vapor degreasers, maintain

a freeboard ratio of 100 percent. The freeboard ratio is equal to the height from the solvent surface to the top of the machine divided by the inside length or width of the tank (whichever is greater) (KSUPPI, 2010).

• Do not fill the cold cleaning or vapor degreasing tank beyond the fill line.

• Rack components in a manner that minimizes drag-out losses. For example, cup-shaped components

should be inverted on the rack.

• Drain cleaned components for at least 15 seconds or until dripping stops. This will limit the escape of

solvent vapors and allow the drained solvent to be recycled back into the cleaning or degreasing tank (KSUPPI, 2010).

• Waste solvents from cold cleaners and vapor degreasers should be collected and stored in closed

containers to keep TCE from evaporating into the workplace. The containers should be properly labeled and managed in accordance with hazardous waste regulations.

• Workers should avoid leaning over a cold cleaning or vapor degreasing tank. Where necessary, use a

hoist to move components in or out of the tank.

• Avoid overloading vapor degreasers. The solvent level should not drop by more than 4 inches when

components are added (KSUPPI, 2010). The introduction of heavy loads will collapse the existing vapor blanket and expel TCE vapors.

• If vapor leaks are detected, repair the vapor degreaser immediately or shut it down until repairs

are made.

### Background Document | 12 DURING product fabrication—particularly for products made from metal—contaminants such as chips, grease, oils, dust, dirt, and polishing pastes can compromise the integrity of the final, fabricated parts (NEWMOA, 2001). For this reason, fabricating shops use degreasers to remove these contaminants, particularly before assembling or painting the final product. Fabrication shops most typically use the following degreasing processes:

• Cold cleaning. Fabricated parts are cleaned by spraying, brushing, flushing, or immersion in a nonboiling (i.e., “cold”) solvent, as shown in Figure 11. Fabrication

of Parts Parts Cleaning Cleaned Parts Direct Sale or Installation into Final Products V APOR D EGREASING

C OLD C LEANING

Figure 11. Cold cleaning system used for cleaning parts.

### Background Document | 13 • Vapor degreasing. Degreasing solvents are boiled to produce a hot vapor (Figure 12). Fabricated

parts are suspended just above the bath, where the condensation of hot vapors cleans them.

After cold cleaning or vapor degreasing, the fabricated parts are suspended on a rack to drain the solvent. Either of these two processes can be done in batches or as part of a conveyorized (i.e., automated) system. With batch work, workers manually load or unload fabricated parts directly into or out of the cleaning solvent. With conveyorized systems, fabricated parts are continuously loaded on a line that automatically passes them through cold cleaning or vapor degreasing equipment as well as the subsequent drying steps 

## Technologies That Eliminate or Reduce Risks from TCE Due to the variety of surfaces and contaminants encountered at fabrication shops, it is difficult to identify specific alternatives that will work across all shops. Choosing the most suitable alternative will depend on the nature of the fabricated parts, their contaminants, and the needed level of cleaning. Further, shops that use cold cleaners have a different set of alternatives than shops that use vapor degreasers. To choose the most appropriate alternative, it is important to evaluate the current cleaning process first. This includes:

• The source of the contaminant. If the contamination occurs at the shop, consider changing the

process to eliminate its source. This would eliminate the need for cleaning parts.

• The types of parts that must be cleaned—specifically the materials of construction (carbon steel,

stainless steel, aluminum, etc.), type of surface (textured or smooth), and shape (simple or complex).

• The types of contaminants that must be removed (heavy oils, light oils, greases, waxes, dirt, salts,

etc.).

• The extent of cleaning needed. Determine the minimum cleanliness specifications for your parts.

Make sure you do not apply more cleaner than is necessary. Once you have evaluated these factors for the shop’s cleaning process, work with vendors to determine which alternatives would best meet your cleaning needs. Figure 12. Vapor degreasing system used for cleaning parts.

### Background Document | 14 

### Water-Based Cleaning This alternative substitutes the use of solvents with water-based chemistries. The degree of substitution can range from completely eliminating solvents (i.e., aqueous cleaning) to partially eliminating solvents (i.e., semi-aqueous cleaning). Water-based cleaning solutions can include various cleaning ingredients such as acid or alkaline chemicals, detergents, water conditioners, corrosion inhibitors, and foam stabilizers (PPRC, 1996a). Parts can be cleaned using the following methods:

• Mechanical cleaning , in which fabricated parts are immersed in the cleaning solution and brushed

clean.

• Spray cleaning , in which fabricated parts are placed in an enclosed chamber and sprayed with the

cleaning solution using high-pressure jets (Figure 13).

• Ultrasonic cleaning , in which fabricated parts are immersed in the cleaning solution and subjected to

high-frequency sound waves that form bubbles on the surface of the parts (Figure 14). The bubbles create a mechanical cleaning action. Figure 13. Spray cleaner that uses an enclosed chamber to prevent worker exposures to the cleaning solution.

Figure 14. Ultrasonic cleaning tank.

### Background Document | 15 

### Closed-Loop Vapor Degreasers If substitution of TCE is not possible for vapor degreasing operations, consider installing a closed-loop vapor degreaser (Figure 15). This system cleans parts in an air-tight chamber, which significantly reduces emissions and can also improve cleaning and product quality. Once the parts are cleaned, vapors are exhausted to the outdoors before the chamber door can be opened. After the vapors are exhausted, workers can open the door and remove the cleaned parts. Compared to conventional open-top vapor degreasers, closed-loop vapor degreasers can reduce vapor emissions by as much as 98 percent (NEWMOA, 2001).

Closed-loop vapor degreasers can incorporate multi-stage processing to enhance cleaning operations. For example, systems are available that can immerse, flush, or spray parts before the vapor degreasing stage, or vice versa. These systems also can incorporate vacuum drying into the process, rather than relying solely on exhaust fans for drying. This not only reduces the drying time but also the potential for worker exposures, since it dries the cleaned parts more thoroughly. 

## Protecting Workers from TCE In protecting your workers, you’ll use engineering controls—protective practices involving technologies and equipment. If it is not possible to eliminate the use of TCE from your cleaning operation, consider installing engineering controls. The control options that apply to fabrication shops will depend on the type of degreasing system used at the shop (i.e., cold cleaner vs. vapor degreaser). The control options listed below will protect workers either by:

• Limiting how much TCE gets released directly into the workplace before it comes into contact with

workers; or

• Limiting how much contact the workers have with TCE after it has been released into the workplace. Generally speaking, the first approach is most desirable, as it not only limits the potential for worker exposures but also the potential for releases into the environment. Figure 15. Closed-loop vapor degreaser.

### Background Document | 16 For cold cleaners and vapor degreasers, the engineering controls listed below focus primarily on limiting how much TCE gets released directly into the workplace before it comes into contact with workers. Some options are available for limiting worker exposures to TCE after it is released into the workplace, but they are limited to the installation of exhaust systems. 

### Cold Cleaners

• For open cleaning tanks, install a vapor-tight cover to limit the escape of solvent vapors whenever

parts are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Cover the solvent bath with a layer of water that is 2 to 4 inches thick. This water cover will float

over the solvent bath and will limit the amount of TCE that evaporates out of the bath and into the workplace (EPA, 1981).

• If using spray equipment, consider using a solid-fluid stream sprayer. Spray pressures should not

exceed 10 pounds per square inch (psi) to avoid unnecessary misting of the cleaning solvent (KSUPPI, 2010). Avoid using atomizing or shower-type sprayers, which can generate more vapors.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing parts from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning parts and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

### Vapor Degreasers

• For open-top degreasers, install a vapor-tight cover to limit the escape of solvent vapors when parts

are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Install a condenser coolant thermostat switch. This switch will automatically shut off the heater

whenever the coolant temperature exceeds the maximum recommended by the equipment manufacturer.

• Install a solvent level control switch. This switch will automatically shut off the heater whenever the

liquid level drops below the minimum recommended by the equipment manufacturer.

• Install a vapor level control switch. This switch will automatically shut off the heater whenever the

vapor level rises above the maximum height recommended by the equipment manufacturer.

• Install a second set of cooling coils. Known as “freeboard chillers,” these coils prevent vapors from

escaping into the workplace. Note that freeboard chillers are not the same as the primary cooling coils that may already be installed in your vapor degreaser. The primary cooling coils are used to adjust the vapor height within the degreaser. They do not provide the same level of protection from vapors as freeboard chillers.

• For air-tight or airless degreasing systems, install a differential pressure gauge. This gauge can be

used to verify that the system is not leaking.

### Background Document | 17 • For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit in order to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing parts from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning parts and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

## Workplace Practices If it is not possible to eliminate the use of TCE from your cold cleaning or vapor degreasing operation, consider implementing the following work practices and administrative controls:

• Cold cleaners and vapor degreasers should be situated in large, open locations with good general

ventilation. These locations should be isolated from the rest of the shop.

• Cold cleaning and vapor degreasing equipment should only be used in accordance with the

equipment manufacturer’s specifications.

• Vapor-tight covers should be closed at all times except during entry and removal of parts.

• When the cover is open, avoid subjecting the tank to direct drafts, particularly from standing fans or

ventilation ducts. These drafts can carry TCE vapors into surrounding work areas.

• For cold cleaners, maintain a freeboard ratio of 75 percent or more. For vapor degreasers, maintain

a freeboard ratio of 100 percent. The freeboard ratio is equal to the height from the solvent surface to the top of the machine divided by the inside length or width of the tank (whichever is greater) (KSUPPI, 2010).

• Do not fill the cold cleaning or vapor degreasing tank beyond the fill line.

• Rack fabricated parts in a manner that minimizes drag-out losses. For example, cup-shaped parts

should be inverted on the rack.

• Drain cleaned parts for at least 15 seconds or until dripping stops. This will limit the escape of solvent

vapors and allow the drained solvent to be recycled back into the cleaning or degreasing tank (KSUPPI, 2010).

• Waste solvents from cold cleaners and vapor degreasers should be collected and stored in closed

containers to keep TCE from evaporating into the workplace. The containers should be properly labeled and managed in accordance with hazardous waste regulations.

• Workers should avoid leaning over a cold cleaning or vapor degreasing tank. Where necessary, use a

hoist to move parts in or out of the tank.

• Avoid overloading vapor degreasers. The solvent level should not drop by more than 4 inches when

parts are added (KSUPPI, 2010). The introduction of heavy loads will collapse the existing vapor blanket and expel TCE vapors.

• If vapor leaks are detected, repair the vapor degreaser immediately or shut it down until repairs are

made.

• For conveyorized cold cleaning or vapor degreasing systems, limit the conveyor speed to no more

than 11 feet per minute so that the cleaned parts have enough time to drain back into the bath (KSUPPI, 2010).

### Background Document | 18 WHILE FABRICATED parts are being electroplated, contaminants such as grease, oils, dust, dirt, and polishing pastes can compromise the electroplated finish, causing cracking and pealing of the metal (NEWMOA, 2001). For this reason, metal plating shops use degreasers to clean the metal surface before electroplating. Metal plating shops most typically use the following degreasing processes:

• Cold cleaning. Parts are cleaned by spraying, brushing, flushing, or immersion in a non-boiling

(i.e., “cold”) solvent, as shown in Figure 16. Receipt of Fabricated Parts Parts Cleaning Parts Electroplating Cleaned Parts Direct Sale of Plated Parts or Final Products V APOR D EGREASING

C OLD C LEANING

+ –

Figure 16. Cold cleaning system used for cleaning parts.

### Background Document | 19 • Vapor degreasing. Degreasing solvents are boiled to produce a hot vapor (Figure 17). Parts are

suspended just above the bath, where the condensation of hot vapors cleans them.

After cold cleaning or vapor degreasing, the parts are rinsed with water and placed in the electroplating bath, where the finishing metal is deposited onto the parts. Either of these two processes can be done in batches or as part of a conveyorized (i.e., automated) system. With batch work, workers manually load or unload parts directly into or out of the cleaning solvent. With conveyorized systems, parts are continuously loaded on a line that automatically passes them through cold cleaning or vapor degreasing equipment as well as the subsequent rinsing, electroplating, and drying steps. 

## Technologies That Eliminate or Reduce Risks from TCE Due to the variety of surfaces and contaminants encountered at metal plating shops, it is difficult to identify specific alternatives that will work across all shops. Choosing the most suitable alternative will depend on the nature of the metal plating parts, their contaminants, and the needed level of cleaning. Further, shops that use cold cleaners have a different set of alternatives than shops that use vapor degreasers. To choose the most appropriate alternative, it is important to evaluate the current cleaning process first. This includes:

• The source of the contaminant. If the contamination occurs at the shop, consider changing the

process to eliminate its source. This would eliminate the need for cleaning parts.

• The types of parts that must be cleaned—specifically the materials of construction (carbon steel,

stainless steel, aluminum, etc.), type of surface (textured or smooth), and shape (simple or complex).

• The types of contaminants that must be removed (heavy oils, light oils, greases, waxes, dirt, salts,

etc.).

• The extent of cleaning needed. Determine the minimum cleanliness specifications for your parts.

Make sure you do not apply more cleaner than is necessary. Figure 17. Vapor degreasing system used for cleaning parts.

### Background Document | 20 Once you have evaluated these factors for the shop’s cleaning process, work with vendors to determine which alternatives would best meet your cleaning needs. 

### Water-Based Cleaning This alternative substitutes the use of solvents with water-based chemistries. The degree of substitution can range from completely eliminating solvents (i.e., aqueous cleaning) to partially eliminating solvents (i.e., semi-aqueous cleaning). Water-based cleaning solutions can include various cleaning ingredients such as acid or alkaline chemicals, detergents, water conditioners, corrosion inhibitors, and foam stabilizers (PPRC, 1996a). Parts can be cleaned using the following methods:

• Mechanical cleaning , in which metal plating parts are immersed in the cleaning solution and brushed

clean.

• Spray cleaning , in which metal plating parts are sprayed with the cleaning solution using highpressure jets (Figure 18).

• Ultrasonic cleaning , in which metal plating parts are immersed in the cleaning solution and subjected

to high-frequency sound waves that form bubbles on the surface of the parts (Figure 19). The bubbles create a mechanical cleaning action. Figure 18. Spray cleaner that uses an enclosed chamber to prevent worker exposures to the cleaning solution.

Figure 19. Ultrasonic cleaning tank.

### Background Document | 21 

### Closed-Loop Vapor Degreasers If substitution of TCE is not possible for vapor degreasing operations, consider installing a closed-loop vapor degreaser (Figure 20). This system cleans parts in an air-tight chamber, which significantly reduces emissions and can also improve cleaning and product quality. Once the parts are cleaned, vapors are exhausted to the outdoors before the chamber door can be opened. After the vapors are exhausted, workers can open the door and remove the cleaned parts. Compared to conventional open-top vapor degreasers, closed-loop vapor degreasers can reduce vapor emissions by as much as 98 percent (NEWMOA, 2001).

Closed-loop vapor degreasers can incorporate multi-stage processing to enhance cleaning operations. For example, systems are available that can immerse, flush, or spray parts before the vapor degreasing stage, or vice versa. These systems also can incorporate vacuum drying into the process, rather than relying solely on exhaust fans for drying. This not only reduces the drying time but also the potential for worker exposures, since it dries the cleaned parts more thoroughly. 

## Protecting Workers from TCE In protecting your workers, you’ll use engineering controls—protective practices involving technologies and equipment. If it is not possible to eliminate the use of TCE from your cleaning operation, consider installing engineering controls. The control options that apply to metal plating shops will depend on the type of degreasing system used at the shop (i.e., cold cleaner vs. vapor degreaser). The control options listed below will protect workers either by:

• Limiting how much TCE gets released directly into the workplace before it comes into contact with

workers; or

• Limiting how much contact the workers have with TCE after it has been released into the workplace. Generally speaking, the first approach is most desirable, as it not only limits the potential for worker exposures but also the potential for releases into the environment. Figure 20. Closed-loop vapor degreaser.

### Background Document | 22 For cold cleaners and vapor degreasers, the engineering controls listed below focus primarily on limiting how much TCE gets released directly into the workplace before it comes into contact with workers. Some options are available for limiting worker exposures to TCE after it is released into the workplace, but they are limited to the installation of exhaust systems. 

### Cold Cleaners

• For open cleaning tanks, install a vapor-tight cover to limit the escape of solvent vapors whenever

parts are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Cover the solvent bath with a layer of water that is 2 to 4 inches thick. This water cover will float

over the solvent bath and will limit the amount of TCE that evaporates out of the bath and into the workplace (EPA, 1981).

• If using spray equipment, consider using a solid-fluid stream sprayer. Spray pressures should not

exceed 10 pounds per square inch (psi) to avoid unnecessary misting of the cleaning solvent (KSUPPI, 2010). Avoid using atomizing or shower-type sprayers, which can generate more vapors.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit in order to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing parts from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning parts and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

### Vapor Degreasers

• For open-top degreasers, install a vapor-tight cover to limit the escape of solvent vapors when parts

are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Install a condenser coolant thermostat switch. This switch will automatically shut off the heater

whenever the coolant temperature exceeds the maximum recommended by the equipment manufacturer.

• Install a solvent level control switch. This switch will automatically shut off the heater whenever the

liquid level drops below the minimum recommended by the equipment manufacturer.

• Install a vapor level control switch. This switch will automatically shut off the heater whenever the

vapor level rises above the maximum height recommended by the equipment manufacturer.

• Install a second set of cooling coils. Known as “freeboard chillers,” these coils prevent vapors from

escaping into the workplace. Note that freeboard chillers are not the same as the primary cooling coils that may already be installed in your vapor degreaser. The primary cooling coils are used to adjust the vapor height within the degreaser. They do not provide the same level of protection from vapors as freeboard chillers.

• For air-tight or air-less degreasing systems, install a differential pressure gauge. This gauge can be

used to verify that the system is not leaking.

### Background Document | 23 • For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit in order to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing parts from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning parts and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

## Workplace Practices If it is not possible to eliminate the use of TCE from your cold cleaning or vapor degreasing operation, consider implementing the following work practices and administrative controls:

• Cold cleaners and vapor degreasers should be situated in large, open locations with good general

ventilation. These locations should be isolated from the rest of the shop.

• Cold cleaning and vapor degreasing equipment should only be used in accordance with the

equipment manufacturer’s specifications.

• Vapor-tight covers should be closed at all times except during entry and removal of parts.

• When the cover is open, avoid subjecting the tank to direct drafts, particularly from standing fans or

ventilation ducts. These drafts can carry TCE vapors into surrounding work areas.

• For cold cleaners, maintain a freeboard ratio of 75 percent or more. For vapor degreasers, maintain

a freeboard ratio of 100 percent. The freeboard ratio is equal to the height from the solvent surface to the top of the machine divided by the inside length or width of the tank (whichever is greater) (KSUPPI, 2010).

• Do not fill the cold cleaning or vapor degreasing tank beyond the fill line.

• Rack parts in a manner that minimizes drag-out losses. For example, cup-shaped parts should be

inverted on the rack.

• Drain cleaned parts for at least 15 seconds or until dripping stops. This will limit the escape of solvent

vapors and allow the drained solvent to be recycled back into the cleaning or degreasing tank (KSUPPI, 2010).

• Waste solvents from cold cleaners and vapor degreasers should be collected and stored in closed

containers to keep TCE from evaporating into the workplace. The containers should be properly labeled and managed in accordance with hazardous waste regulations.

• Workers should avoid leaning over a cold cleaning or vapor degreasing tank. Where necessary, use a

hoist to move parts in or out of the tank.

• Avoid overloading vapor degreasers. The solvent level should not drop by more than 4 inches when

parts are added (KSUPPI, 2010). The introduction of heavy loads will collapse the existing vapor blanket and expel TCE vapors.

• If vapor leaks are detected, repair the vapor degreaser immediately or shut it down until repairs are

made.

• For conveyorized cold cleaning or vapor degreasing systems, limit the conveyor speed to no more

than 11 feet per minute so that the cleaned parts have enough time to drain back into the bath (KSUPPI, 2010).

### Background Document | 24 DURING ELECTRONICS ASSEMBLY , electronic components are attached to a circuit board and soldered in place, permanently connecting them to the board. Just before soldering, flux is applied to the board to clean the surface and to prevent contamination during soldering. The flux is then cleaned from the board using TCE. Electronics assembly shops most typically use the following degreasing processes:

• Cold cleaning. Electronics are cleaned by spraying, brushing, flushing, or immersion in a non-boiling

(i.e., “cold”) solvent, as shown in Figure 21. Fabrication of Circuit Board Assemblies Circuit Board Assembly Cleaning Cleaned Circuit Board Assemblies Direct Sale or Installation Into Final Products V APOR D EGREASING

C OLD C LEANING

Figure 21. Cold cleaning system used for cleaning components.

### Background Document | 25 • Vapor degreasing. DDegreasing solvents are boiled to produce a hot vapor (Figure 22). Electronics

are suspended just above the bath, where the condensation of hot vapors cleans them.

After cold cleaning or vapor degreasing, the components are dried and assembled to produce the finished electronic device. Either of these two processes can be done in batches or as part of a conveyorized (i.e., automated) system. With batch work, workers manually load or unload components directly into or out of the cleaning solvent. With conveyorized systems, components are continuously loaded on a line that automatically passes them through cold cleaning or vapor degreasing equipment as well as the subsequent drying steps. 

## Technologies That Eliminate or Reduce Risks from TCE Due to the variety of components and contaminants encountered at electronics assembly shops, it is difficult to identify specific alternatives that will work across all shops. Choosing the most suitable alternative will depend on the nature of the electronic assemblies, their contaminants, and the needed level of cleaning. Further, the cleaning processes already in use at a given shop will determine what alternatives are available. To choose the most appropriate alternative, it is important to evaluate the current cleaning process first. This includes:

• The source of the contaminant. If the contamination occurs at the shop, consider changing the

process to eliminate its source. This would eliminate the need for cleaning components.

• The types of parts that must be cleaned—specifically the type of surface (textured or smooth) and

shape (simple or complex).

• The types of contaminants that must be removed (heavy oils, light oils, greases, waxes, dirt,

salts, etc.).

• The extent of cleaning needed. Determine the minimum cleanliness specifications for your

components. Make sure you do not apply more cleaner than is necessary. Figure 22. Vapor degreasing system used for cleaning components.

### Background Document | 26 Once you have evaluated these factors for the shop’s cleaning process, work with vendors to determine which alternatives would best meet your cleaning needs. 

### Low-Solids Fluxes Low-solids fluxes are used in the same way as conventional fluxes. However, their residues dry rapidly, leaving behind little or no residues on the circuit boards; this eliminates the need for solvent cleaning. The successful application of low-solids fluxes will depend on the specific needs of the electronic component being assembled. For some components, even trace amounts of residues will compromise the reliability of the electronics (EPA, 1996); therefore, these fluxes should only be used on components that are not sensitive to flux residues. 

### Inert Atmosphere Soldering In inert atmosphere soldering, the soldering station is placed in an oxygen-free environment—typically nitrogen gas. The inert environment prevents the production of oxide contaminants during soldering, thereby eliminating the need for any flux or subsequent solvent cleaning steps. As with low-solids flux technology, the suitability of inert atmosphere soldering depends on the specific needs of the electronic component being assembled, as some components can still require flux before soldering even if an inert environment is used (EPA, 1994). 

### Water-Based Cleaning This alternative substitutes the use of solvents with water-based chemistries. The degree of substitution can range from completely eliminating solvents (i.e., aqueous cleaning) to partially eliminating solvents (i.e., semi-aqueous cleaning). Water-based cleaning solutions can include various cleaning ingredients such as acid or alkaline chemicals, detergents, water conditioners, corrosion inhibitors, and foam stabilizers (PPRC, 1996a). Components can be cleaned using the following methods:

• Mechanical cleaning , in which electronic components are immersed in the cleaning solution and

brushed clean.

• Spray cleaning , in which components are placed in an enclosed chamber and sprayed with the

cleaning solution using high-pressure jets (Figure 23).

Figure 23. Spray cleaner that uses an enclosed chamber to prevent worker exposures to the cleaning solution.

### Background Document | 27 • Ultrasonic cleaning , in which electronic components are immersed in the cleaning solution and

subjected to high-frequency sound waves that form bubbles on the surface of the components (Figure 24). The bubbles create a mechanical cleaning action.



### Closed-Loop Vapor Degreasers If substitution of TCE is not possible for vapor degreasing operations, consider installing a closed-loop vapor degreaser (Figure 25). This system cleans components in an air-tight chamber, which significantly reduces emissions and can also improve cleaning and product quality. Once the components are cleaned, vapors are exhausted to the outdoors before the chamber door can be opened. After the vapors are exhausted, workers can open the door and remove the cleaned components. Compared to conventional open-top vapor degreasers, closed-loop vapor degreasers can reduce vapor emissions by as much as 98 percent (NEWMOA, 2001).

Closed-loop vapor degreasers can incorporate multi-stage processing to enhance cleaning operations. For example, systems are available that can immerse, flush, or spray components before the vapor degreasing stage, or vice versa. These systems also can incorporate vacuum drying into the process, rather than relying solely on exhaust fans for drying. This not only reduces the drying time but also the potential for worker exposures, since it dries the cleaned components more thoroughly. Figure 24. Ultrasonic cleaning tank.

Figure 25. Closed-loop vapor degreaser.

### Background Document | 28 

## Protecting Workers from TCE In protecting your workers, you’ll use engineering controls—protective practices involving technologies and equipment. If it is not possible to eliminate the use of TCE from your cleaning operation, consider installing engineering controls. The control options that apply to electronics assembly shops will depend on the type of degreasing system used at the shop (i.e., cold cleaner vs. vapor degreaser). The control options listed below will protect workers either by:

• Limiting how much TCE gets released directly into the workplace before it comes into contact with

workers; or

• Limiting how much contact the workers have with TCE after it has been released into the workplace. Generally speaking, the first approach is most desirable, as it not only limits the potential for worker exposures but also the potential for releases into the environment. For cold cleaners and vapor degreasers, the engineering controls listed below focus primarily on limiting how much TCE gets released directly into the workplace before it comes into contact with workers. Some options are available for limiting worker exposures to TCE after it is released into the workplace, but they are limited to the installation of exhaust systems. 

### Cold Cleaners

• For open cleaning tanks, install a vapor-tight cover to limit the escape of solvent vapors whenever

components are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Cover the solvent bath with a layer of water that is 2 to 4 inches thick. This water cover will float

over the solvent bath and will limit the amount of TCE that evaporates out of the bath and into the workplace (EPA, 1981).

• If using spray equipment, consider using a solid-fluid stream sprayer. Spray pressures should not

exceed 10 pounds per square inch (psi) to avoid unnecessary misting of the cleaning solvent (KSUPPI, 2010). Avoid using atomizing or shower-type sprayers, which can generate more vapors.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit in order to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing components from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning components and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

### Vapor Degreasers

• For open-top degreasers, install a vapor-tight cover to limit the escape of solvent vapors when

components are not being cleaned. Rolling covers are preferable over hinged covers, since hinged covers can force the escape of TCE vapors when they swing closed.

• Install a condenser coolant thermostat switch. This switch will automatically shut off the heater

whenever the coolant temperature exceeds the maximum recommended by the equipment manufacturer.

### Background Document | 29 • Install a solvent level control switch. This switch will automatically shut off the heater whenever the

liquid level drops below the minimum recommended by the equipment manufacturer.

• Install a vapor level control switch. This switch will automatically shut off the heater whenever the

vapor level rises above the maximum height recommended by the equipment manufacturer.

• Install a second set of cooling coils. Known as “freeboard chillers,” these coils prevent vapors from

escaping into the workplace. Note that freeboard chillers are not the same as the primary cooling coils that may already be installed in your vapor degreaser. The primary cooling coils are used to adjust the vapor height within the degreaser. They do not provide the same level of protection from vapors as freeboard chillers.

• For air-tight or air-less degreasing systems, install a differential pressure gauge. This gauge can be

used to verify that the system is not leaking.

• For cleaning tanks with surface areas exceeding 10 square feet, install a lateral exhaust system (MM,

no date). The exhaust should pass through a carbon adsorption unit to reduce the amount of solvent that exhausts to the outdoors. Under no circumstances should the exhaust system re-circulate back into the workplace.

• For conveyorized systems, install a drying tunnel or rotating/tumbling basket. This will reduce the

amount of solvent liquid dragged out of the cleaning bath and reduce the amount of vapor that workers could inhale when removing components from the basket.

• For conveyorized systems, minimize the size of the cleaning unit’s openings. The average clearance

between cleaning components and the edge of the cleaning unit’s opening should not exceed 10 percent of the opening’s width (KSUPPI, 2010). 

## Workplace Practices If it is not possible to eliminate the use of TCE from your cold cleaning or vapor degreasing operation, consider implementing the following work practices and administrative controls:

• Cold cleaning or vapor degreasing should never take place in the same room as soldering operations.

Soldering operations generate intense heat that can decompose the solvent vapors to produce phosgene, a gas that is even more toxic than TCE (NOHSC, 1989).

• Cold cleaners and vapor degreasers should be situated in large, open locations with good general

ventilation. These locations should be isolated from the rest of the shop.

• Cold cleaning and vapor degreasing equipment should only be used in accordance with the

equipment manufacturer’s specifications.

• Vapor-tight covers should be closed at all times except during entry and removal of components.

• When the cover is open, avoid subjecting the tank to direct drafts, particularly from standing fans or

ventilation ducts. These drafts can carry TCE vapors into surrounding work areas.

• For cold cleaners, maintain a freeboard ratio of 75 percent or more. For vapor degreasers, maintain

a freeboard ratio of 100 percent. The freeboard ratio is equal to the height from the solvent surface to the top of the machine divided by the inside length or width of the tank (whichever is greater) (KSUPPI, 2010).

• Do not fill the cold cleaning or vapor degreasing tank beyond the fill line.

• Rack components in a manner that minimizes drag-out losses. For example, cup-shaped components

should be inverted on the rack.

### Background Document | 30 • Drain cleaned components for at least 15 seconds or until dripping stops. This will limit the escape of

solvent vapors and allow the drained solvent to be recycled back into the cleaning or degreasing tank (KSUPPI, 2010).

• Waste solvents from cold cleaners and vapor degreasers should be collected and stored in closed

containers to keep TCE from evaporating into the workplace. The containers should be properly labeled and managed in accordance with hazardous waste regulations.

• Workers should avoid leaning over a cold cleaning or vapor degreasing tank. Where necessary, use a

hoist to move components in or out of the tank.

• Avoid overloading vapor degreasers. The solvent level should not drop by more than 4 inches when

components are added (KSUPPI, 2010). The introduction of heavy loads will collapse the existing vapor blanket and expel TCE vapors.

• If vapor leaks are detected, repair the vapor degreaser immediately or shut it down until repairs are

made.

• For conveyorized cold cleaning or vapor degreasing systems, limit the conveyor speed to no more

than 11 feet per minute so that the cleaned components have enough time to drain back into the bath (KSUPPI, 2010).

### Background Document | 31 

# R efe r ences

(ATSDR, 1997) Toxicological Profile for Trichloroethylene . U.S. Agency for Toxic Substances and Disease Registry, Division of Toxicology, Toxicology Information Branch, Atlanta, GA. 1997. Available at: www.epa.gov/iris/supdocs/0199index.html

. (EPA, no date) Evaluation of Alternatives to Chlorinated Solvents for Metal Cleaning . U.S. Environmental Protection Agency. No date. (EPA, 1981) Solvent Degreasing . AP-42 – Compilation of Air Pollutant Emission Factors. Vol. 1. Fifth Ed. U.S. Environmental Protection Agency. 1981. (EPA, 1991) Guides to Pollution Prevention—The Automotive Repair Industry . U.S. Environmental Protection Agency. 1991. (EPA, 1994) Guide to Cleaner Technologies—Cleaning and Degreasing Process Changes . U.S. Environmental Protection Agency. 1994. (EPA, 1996) Pollution Prevention in the Electronics Industry . U.S. Environmental Protection Agency. 1996. (EPA, 2001) Guide to Industrial Assessments for Pollution Prevention and Energy Efficiency . U.S. Environmental Protection Agency. 2001. (EPA, 2011) Toxicological Review of Trichloroethylene (CAS No. 79-01-6) . EPA/635/R-09/011F. U.S. Environmental Protection Agency, Integrated Risk Information System, Office of Research and Development, Washington, DC. 2011. Available at: www.epa.gov/iris/ supdocs/0199index.html

. (HSIA, no date) Trichloroethylene . Halogenated Solvents Industry Alliance. No date. (KSUPPI, no date a) Pollution Prevention for the Automotive Maintenance and Repair Industry . Kansas State University Pollution Prevention Institute. No date. (KSUPPI, no date b) Pollution Prevention for the Electroplating and Metal Finishing Industry . Kansas State University Pollution Prevention Institute. No date. (KSUPPI, 2010) The Smell of Success: Decreasing Air Pollution in the Kansas City Area . Kansas State University Pollution Prevention Institute. 2010. (MM, no date) Guidelines on Solvent Degreasing. Singapore Ministry of Manpower. No date. Available at: www.mom.gov.sg/Documents/safety-health/factsheets-circulars/Solvent%20 Degreasing.pdf

. (NEWMOA, 2001) Pollution Prevention Technology Profile – Closed Loop Vapor Degreasing . Northeast Waste Management Officials’ Association. 2001. (NIOSH, 2011) Trichloroethylene . NIOSH Pocket Guide to Chemical Hazards. National Institute for Occupational Safety and Health. 2011. Available at: www.cdc.gov/niosh/npg/npgd0629. html

. (NJDH, 2008) Right to Know Hazardous Substance Fact Sheet: Trichloroethylene . New Jersey Department of Health. 2008. Available at: http://nj.gov/health/eoh/rtkweb/documents/ fs/1890.pdf

.

### Background Document | 32 (NOHSC, 1989) Solvent Vapor Degreasing . Australia National Occupational Health and Safety Commission. 1989. Available at: www.safeworkaustralia.gov.au/sites/SWA/about/ Publications/Documents/160/SolventVapourDegreasing_1989_PDF.pdf

. (NYSDEC, 2003) Environmental Compliance, Pollution Prevention and Self-Assessment Guide for Vehicle Maintenance Shops . New York State Department of Environmental Conservation. 2003. (Pecht, 2003) Pecht, M. et al. Contamination of Electronic Assemblies . CRC Press LLC. 2003. (PPRC, 1996a) Aqueous Cleaning Technology Review . Pacific Northwest Pollution Prevention Resource Center. 1996a. Available at: www.pprc.org/pubs/techreviews/aqueous/aqintro.html

. (PPRC, 1996b) No-Clean Technology Review . Pacific Northwest Pollution Prevention Resource Center. 1996b. Available at: www.pprc.org/pubs/techreviews/noclean/nointro.html

. (TURI, 1995) Closed Loop Aqueous Cleaning . The Massachusetts Toxics Use Reduction Institute, University of Massachusetts Lowell. 1995. (TURI, 1997) Guidebook of Part Cleaning Alternatives. The Massachusetts Toxics Use Reduction Institute, University of Massachusetts Lowell. 1997.