Code of Practice for reducing dichloromethane emissions from use of paint strippers: chapter 2

Official title: Code of practice for the reduction of dichloromethane emissions from the use of paint strippers in commercial furniture refinishing and other stripping applications

2.0 Code of practice for miscellaneous commercial paint stripping facilities

2.1 Applicability

Part 2 of the code of practice applies to (i) metal parts paint strippers, (ii) auto body shops, and (iii) building restoration firms. Not all work practices identified in this section are appropriate for every facility. Each commercial paint stripper should review the code and implement those work practices appropriate to its specific situation. The work practices that reduce the dichloromethane evaporation rate will also serve to minimize paint stripper waste, thus reducing the facility's overall operating costs.

Several of the work practices identified in this section may apply to facilities that provide commercial paint stripping services in areas other than those identified above.

2.2 General recommended work practices - commercial metal parts stripping facilities

Work practices outlined in this section refer to commercial paint strippers that utilize a dip tank to strip the paint from metal parts. Consider equipping dip tanks or any tanks containing dichloromethane-based paint stripper with dikes and a drain containment system with sufficient capacity to contain spills or leaks before they evaporate.

2.2.1 Evaluate non-dichloromethane-based paint stripping alternatives

Some alternatives to dichloromethane-based paint strippers include thermal stripping, caustic stripping, and media blasting. Any alternative should be thoroughly evaluated before being employed. All possible benefits and drawbacks of each alternative should be compared with those of using dichloromethane-based paint strippers before a decision is made.

2.2.2 Use paint strippers with lower dichloromethane content when possible

Paint strippers used by metal cleaning facilities generally contain approximately 70-90% dichloromethane. Whenever possible, it is recommended to use paint strippers with a lower dichloromethane content.

Lower dichloromethane content paint strippers will not in all instances result in reduced dichloromethane emissions. Therefore, each facility should evaluate its own unique situation and the potential benefits, if any, of using paint strippers with a lower dichloromethane content.

Lower dichloromethane content paint strippers may not remove the paint from metal parts as rapidly as paint strippers with a higher dichloromethane content. Therefore, use lower content dichloromethane-based paint strippers when time allows and when additional quantities of the paint stripper will not be necessary. Additional applications would offset the benefits of using a lower content dichloromethane-based paint stripper.

2.2.3 Clean metal parts prior to stripping

Material caught in crevices may prevent the paint stripper from removing all of the paint from the metal surface. The metal part may have to be submersed in the dip tank again in order to completely remove all of the paint.

2.2.4 Ensure that dip tanks are properly fitted with lids

Dip tanks should be fitted with lids. Keep the lid on the dip tank whenever possible. Lids should be opened only when placing metal parts in or taking metal parts out of the dip tank. Close the lid on the dip tank immediately after the metal part has been lowered into or taken out of the dip tank. Keeping the lid closed on the dip tank whenever possible reduces contact between the paint stripper and the surrounding air, therefore minimizing dichloromethane emissions. Lids for dip tanks may be constructed of several different materials. Stainless steel is the most desirable, but other metals (such as galvanized metals) may work as well. Plywood or polypropylene lids can be used, but they may retain dichloromethane through absorption or diffusion and release vapours over time.

Minimize the gap between the lid and the dip tank. Lids for dip tanks may warp due to normal wear and tear. Reducing the gap between the lid and the dip tank will reduce the level of evaporation and will likely reduce dichloromethane emissions.

Opening and closing the lid to the dip tank generates air disturbances over the surface of the paint stripper in the tank and results in dichloromethane emissions. Minimize the number of times the tank lid is opened and the duration that the lid remains open each time. Gently opening and closing the lid could reduce the air disturbance, which should reduce dichloromethane emissions. To further minimize air disturbance, fit dip tanks with sliding covers.

2.2.5 Use water to form a seal on top of the paint stripper when appropriate

A water seal may not be appropriate in all cases, as it may react with the accelerators in the paint stripper, possibly reducing the efficiency of the paint stripper. Users should confirm compatibility before considering a water seal.

Water seals added on top of the paint stripper in the dip tank form a barrier between the paint stripper and the surrounding air. The depth of the water seal will depend on the size of the metal parts that the dip tank can accommodate. Facilities should evaluate the most effective depth for the water seal, but a water layer of 10 centimetres (cm) (4 inches) should properly seal most dip tank designs.

Introducing metal parts to and removing metal parts from the dip tank will break the water seal and expose the paint stripper to the surrounding air.

2.2.6 Use inert floating balls to form a seal on top of the paint stripper when appropriate

Inert floating balls (forexample, Teflon® balls) that are 1.5-2.5 cm (0.5-1 inch) in diameter can be added to the dip tank so that they float on top of the paint stripper. The inert balls create a barrier and reduce the surface area of the paint stripper exposed to the surrounding air. These balls should not absorb paint stripper. Users of this method should ensure that the balls are compatible with the paint stripper and that they are clean, so that the paint stripper does not adhere to contamination on the balls. The number of inert balls added to the dip tank will depend on the dimensions of the dip tank.

Inert balls can be accidentally removed when extracting metal parts from the dip tank. It is recommended to clean these balls immediately and return them to the dip tank.

2.2.7 Reduce the surface area of the dip tank

It is recommended to minimize the surface area of the paint stripper in the dip tank as much as possible. Dip tanks come in various sizes (height, width, length). Using a deeper dip tank that is shorter and narrower will reduce the surface area of the exposed paint stripper in the dip tank. Minimizing surface area should reduce the amount of paint stripper in contact with the surrounding air, which will likely minimize emissions.

2.2.8 Place metal parts strategically on the rack to be lowered into the dip tank

Avoid placing metal parts on the rack in such a way that they fill with paint stripper. The paint stripper will not be able to drain from the parts back into the dip tank if the liquid is captured in the metal part. Stand concave metal parts on end to ensure that the paint stripper drains off when the parts are removed from the dip tank. Hollow metal parts should be placed with the cavity facing downward so that the paint stripper drains out of the part when it is removed from the dip tank.

2.2.9 Let excess paint stripper drip from the metal part

Drain metal parts removed from the dip tank until most of the paint stripper has dripped back into the tank. The time needed for the paint stripper to drain from the metal part back into the dip tank will depend upon the configuration of the part being stripped.

The rack holding the metal parts can be lifted out of the dip tank in steps (for example, a few centimetres or inches at a time). Removing the rack in steps allows the rack to be agitated or jarred so that more of the paint stripper may be released from the part and allowed to drip back into the dip tank. Removing the rack in a fluid motion may not recapture as much of the paint stripper.

2.2.10 Evaluate the use of paint strippers that contain a wax additive

Evaluate the use of paint stripping formulations that contain a wax additive. The wax will harden on the top of the paint stripping formulation when applied. The solidified wax forms a barrier on the exterior of the metal part, which reduces contact between the dichloromethane in the paint stripper and the surrounding air, thus likely reducing emissions.

2.2.11 Maintain the quantity of paint stripper in the dip tank at the lowest possible level

Emissions of dichloromethane can occur when air flows over the paint stripper in an open dip tank and the dichloromethane evaporates. Keeping as much of the paint stripper as possible in a sealed storage container, and only the minimum amount of paint stripper necessary in the dip tank, will reduce exposure of the paint stripper to air and will likely reduce emissions of dichloromethane. In operations with a high rate of air flow, extend the sides of the dip tank vertically. Longer vertical sides will create a deeper dip tank, which will reduce the amount of surrounding air that contacts the paint stripper.

2.2.12 Minimize contact with air when introducing new paint stripper

It is recommended to use a valve and hose system to introduce new paint stripper from the storage container to the dip tank. Place the end of the hose below the surface of the paint stripping solution. This system will allow the paint stripper to flow into the dip tank with reduced exposure to the surrounding air. This also minimizes disturbance to the surface of the paint stripper in the dip tank.

2.2.13 Recycle dichloromethane removed in the rinsing process

Use a recycling system to capture dichloromethane where feasible. This recycling system captures dichloromethane that is still contained on the stripped metal part after removal from the dip tank. After removing metal parts from the dip tank, submerse them in a rinsing tank instead of spraying them to remove paint chips and excess paint stripper. Since dichloromethane has low water solubility and is denser than water, excess dichloromethane remaining on the metal part settles to the bottom of the rinsing tank. The dichloromethane can then be removed from the bottom of the rinsing tank through a valve opening and internally recycled or sent to a recycler to be reclaimed. Very little, if any, of the dichloromethane evaporates when in the rinsing tank because of the water barrier in the tank.

Pumps should be used to remove spent paint stripper from the dip tank and into drums without exposing the dichloromethane to the surrounding air. This pumping system can also be used to remove dichloromethane that has settled to the bottom in the rinsing tank.

2.2.14 Assess the feasibility of venting the air around the dip tank through activated carbon

The air flow above the dip tank can be directed through an activated carbon filter to trap dichloromethane. This work practice may be more viable for large operations that have high concentrations of dichloromethane in the air surrounding the dip tank. Properly handle and regularly dispose of the carbon containing dichloromethane.

2.3 General recommended auto body shops

Work practices outlined in this section refer to auto body shops that utilize paint strippers to remove coatings from various auto body surfaces. This code of practice addresses gel- and aerosol-based paint strippers, which are typically used by auto body shops.

2.3.1 Evaluate the use of non-dichloromethane-based alternatives or lower dichloromethane content paint stripping alternatives

Some non-dichloromethane paint stripping alternatives used in auto body shops include sanding and media blasting. Any alternative should be thoroughly evaluated before being employed. All possible benefits and drawbacks of each alternative should be compared with those of using dichloromethane-based paint strippers before a decision is made.

Paint strippers used by auto body shops generally contain approximately 70-85% dichloromethane. Whenever applicable, it is recommended to use paint strippers with a lower dichloromethane content.

It is important to note that lower dichloromethane content paint strippers may not remove the paint from auto body surfaces as rapidly as paint strippers with a higher dichloromethane content. This may result in the use of larger quantities of lower content dichloromethane-based paint strippers. Therefore, lower dichloromethane content paint strippers will not always result in reduced dichloromethane emissions. Each facility should evaluate its own particular situation and the potential benefits and drawbacks of using paint strippers with a lower dichloromethane content.

2.3.2 Sand the surface before applying paint stripper

Sanding the area to be stripped before applying the paint stripper will remove the clearcoat on the auto body surface. Sanding the clearcoat reduces the quantity of paint stripper required, as fewer coating layers will have to be removed. In addition, sanding will also allow the paint stripper to penetrate the coating layers more easily.

It is recommended to make minute scratches with sandpaper in the coatings that are to be stripped so that, when the paint stripper is applied, the grooves channel the paint stripper. This will reduce the amount of paint stripper wasted on areas that do not need it.

2.3.3 Apply masking tape over crevices in the auto body surface

Masking tape can be applied to cover the crevices between the hood and the side of the car to ensure that the paint stripper does not run under the hood. Masking tape can also ensure that the paint stripper does not flow onto painted sections of the auto body that are not meant to be stripped.

When stripping large surfaces (for example, the hood), evaluate the effectiveness of constructing an elevated border to channel the paint stripper over the desired areas. This would effectively prohibit access to the areas of the automobile that are not to be stripped, reducing the amount of wasted paint stripper.

2.3.4 Brush paint strippers onto the surface in one direction

Paint strippers should not be applied onto the auto body surface in back and forth strokes, as this disturbs the wax seal that forms on the vehicle surface. Disturbing the wax seal results in exposure of the dichloromethane in the paint stripper to the surrounding air, which increases the dichloromethane evaporation rate. Air also becomes entrained in the paint stripper, reducing contact between the dichloromethane and the surface area to be stripped. Excessive brushing will reduce the effectiveness of the paint stripper.

2.3.5 Apply paint strippers to workable surface areas

Paint stripper should be applied in small, workable areas that will allow the paint to be removed before the paint stripper dries. The size of the workable area will depend on the experience of the individual applying the paint stripper.

The dichloromethane and other solvents in the paint stripper will eventually evaporate and cause the applied paint stripper to dry out. Should this happen prior to removal of the paint surface, an additional application of paint stripper will be required.

The manufacturer's recommended rate guidelines for paint stripper application should be considered, as they are expected to minimize the number of occasions on which the paint stripper dries before the paint is scraped from the surface.

2.3.6 Leave the paint stripper on the surface for a sufficient length of time

The softening of the coating on the auto body surface signifies that the paint stripper and the coatings are ready to be removed. Scraping the paint stripper off the vehicle surface prior to this softening reaction risks leaving some of the coating in place. An additional application of the paint stripper will then be required to remove the remaining coating.

2.3.7 Remove paint stripper from storage containers in small quantities

Unused gel-based paint stripper is not typically returned to its storage container once the stripping job is complete. Due to evaporation of the dichloromethane and other solvents, the returned paint stripper would not have the same properties as the new paint stripper in the storage container. Therefore, unused paint stripper is typically disposed of. Removing small amounts from the storage container as required will minimize the quantity of paint stripper wasted.

2.3.8 Use gel-based instead of aerosol-based paint strippers whenever possible

Gel-based paint strippers should be applied instead of aerosol-based paint strippers whenever possible.

The size of certain auto body parts (for example, grill) results in large quantities of the aerosol paint stripper being sprayed onto areas that are not to be stripped, therefore wasting the product. In these instances, a gel-based paint stripper should be used. Aerosol-based paint strippers are also generally harder to control than gel-based paint strippers. The fan of the aerosol spray is difficult to direct, and often some spray enters other areas (for example, the air). Using a gel-based paint stripper allows better control and more effective and efficient application of the paint stripper to the desired surface area. Some areas on the auto body surface (for example, crevices) may be better suited for aerosol-based paint strippers, since it is difficult to apply the gel-based paint stripper to these areas.

2.3.9 Capture and reuse gel-based paint stripper where applicable

Stripping vertical auto body surfaces or surfaces that are close to the floor may cause gel-based paint stripper to drip onto the floor. If these drippings are caught on metal/plastic trays, they can be reapplied to the surface being stripped. This will reduce the quantity of new paint stripper used.

Thicker gel-based paint stripper should be used when stripping vertical auto body surfaces or surfaces close to the floor. Thicker gel-based paint stripper will be less likely to drip onto the floor and be wasted.

2.3.10 Follow manufacturer/supplier's recommendations for optimum application temperature

Some manufacturers of auto body paint strippers have suggested that optimum paint stripping results can be achieved when the auto body surface is heated to a temperature of 32-40°C before the paint stripper is applied. This is because paint strippers work faster when applied to a heated surface. However, the paint stripper will dry more quickly if the surface is heated. Only small areas of the automobile surface should be preheated at a time to ensure that the paint can be removed before the paint stripper dries. The manufacturer/supplier of the paint stripper used should be contacted to identify the optimum temperature range. This information may be contained in the application instructions printed on the paint stripper container.

2.4 General recommended building restoration

Work practices outlined in this section refer to building restoration firms that utilize paint strippers to remove coatings from various building surfaces, such as floors, porch railings, and walls. The use of paint strippers to remove graffiti from building surfaces is another important application. This code of practice addresses gel-based paint strippers, which are typically used by building restoration firms.

2.4.1 Evaluate the use of non-dichloromethane-based or lower dichloromethane content paint stripping alternatives

Some non-dichloromethane paint stripping alternatives used by building restoration firms include alcohol-based strippers and caustic strippers. Any alternative should be thoroughly evaluated before being employed. All possible benefits and drawbacks of each alternative should be compared with those of using dichloromethane-based paint strippers before a decision is made.

Paint strippers used by building restoration firms generally contain approximately 35-75% dichloromethane. Whenever applicable, it is recommended to use paint strippers with a lower dichloromethane content. It is important to note that lower dichloromethane content paint strippers may not remove the paint from building surfaces as rapidly as paint strippers with a higher dichloromethane content. This may result in the use of larger quantities of lower content dichloromethane-based paint strippers. Therefore, lower dichloromethane content paint strippers will not always result in reduced dichloromethane emissions. Each facility should evaluate its own particular situation and the potential benefits and drawbacks of using paint strippers with a lower dichloromethane content.

2.4.2 Use chemical-resistant sheeting where possible to reduce evaporation rate

Once the paint stripper is applied, the surface in question should be covered with chemical-resistant sheeting (for example, polypropylene, nylon). Tape down the corners of the chemical-resistant sheeting. The use of protective sheeting will extend the paint stripper drying time and help the stripper to penetrate the coatings. This will increase the effectiveness of the paint stripper, so that more paint is stripped off and less additional paint stripper will be required to finish the job.

2.4.3 Distribute paint stripper evenly over the surface area to be stripped

Applying an even coat of paint stripper ensures that the entire surface receives the same quantity of paint stripper and that no area will dry more quickly than others.

2.4.4 Perform a test with the paint stripper on the surface area to be stripped

It is recommended to test the surface to be stripped to determine the quantity of paint stripper that will be required to remove the coatings. When performing a test, ensure that the test area reflects the entire surface in question. Non-dichloromethane-based paint strippers can also be tested to determine if they would work on the surface being stripped. Testing the surface area will determine the optimum amount of paint stripper to be applied to remove the coatings. This should reduce the need for application of additional paint stripper. If alternative paint strippers prove to be effective in the test, the use of the dichloromethane-based paint stripper can be avoided.

If there are other areas of the project in which different or additional coatings are suspected, then a test zone of that area would also be warranted.

2.4.5 Apply paint strippers to workable surface areas

Paint stripper should be applied in small, workable areas that will allow the paint to be removed before the paint stripper dries. The dichloromethane and other solvents in the paint stripper will eventually evaporate and cause the applied stripper to dry. Should this occur before the paint surface is removed, an additional application of paint stripper will be required.

Applying the manufacturer's recommended amount will likely minimize the number of occasions on which the paint stripper dries before the paint is removed from the surface.

2.4.6 Maintain optimum working conditions for the paint stripper

Dichloromethane dries more quickly if the surface being stripped is heated - for instance, if it is in direct sunlight. Paint strippers dry more slowly and maintain their effectiveness for longer periods on cooler and shaded surfaces. When applying dichloromethane-based paint strippers to large areas (as in building restoration), the surface should be cool and shaded to prevent the paint stripper from drying before it can be removed. The optimum ambient temperature when working with paint strippers is between 13°C and 24°C.

2.5 Recommendations for paint stripper handling and storage

Storage and handling information is communicated on the Material Safety Data Sheets. Refer to these sheets for further instructions.

• Ship paint stripper in closed, airtight containers.
• It is recommended to keep the lids on paint stripper containers tightly closed at all times. Refasten paint stripper container lids immediately after paint stripper is removed from the container.
• Paint stripper containers should be stored in a cool, dry, well-ventilated location. Exposure to high temperatures or to the sun may cause paint stripper containers to leak or swell.
• Try to remove as much of the paint stripper from its storage container as possible before disposing of the storage container.
• When filling smaller vessels from the larger paint stripper storage container, keep the tap near, if not in, the entry hole to reduce exposure to the surrounding air.
• All handling and storage activities should be in compliance with local regulations, such as provincial fire codes, etc.
• Consider equipping storage tanks containing dichloromethane-based paint stripper with dikes and a drain containment system with sufficient capacity to contain spills or leaks before they evaporate.

2.6 Recommendations for waste handling and disposal

Hazardous waste disposal information is communicated on the Material Safety Data Sheets. Refer to these sheets for further instruction.

• It is recommended to dispose of empty, non-returnable containers immediately using an approved method. Treat the containers as waste or hazardous waste as appropriate. Local solid waste authorities can usually assist with this.
• All waste handling and disposal should be in compliance with local, provincial, aboriginal, territorial, and federal regulations, such as the Transportation of Dangerous Goods Act. Note that generators of hazardous waste may require registration with provincial or territorial authorities.
• If a container is to be used to accumulate material for recycling or waste disposal, it should be stored with lids and all other openings tightly sealed after every addition.
• Ship waste or recyclable materials in closed, airtight containers.
• After the paint stripping process, collect materials soaked with paint stripper and transfer them immediately to the designated waste storage container. Dispose of this waste through a government authorized waste disposal or processing company. Suppliers of paint stripper may have a collection service for contaminated paint stripper. Contact the local county, municipal, provincial or territorial government authority for instructions on disposal.
• It may be possible to wipe the stripped surface down with a damp (with water or lacquer thinner) cloth, steel wool pad, or stiff bristle brush instead of hosing down the surface. This will avoid the introduction of paint stripper residue and dichloromethane into the municipal wastewater system. Place the used scrubbing materials (for example, brush, cloth, etc.) in a sealed storage container after use, and dispose of them according to the environmental requirements of the local municipal authority.

2.7 Recommendations for record-keeping

The information required in this section should be kept for three years to track paint stripper use and to help develop an internal dichloromethane emission reduction system.

• It is recommended to record specific actions implemented to reduce the quantity of paint stripper used or the quantity of dichloromethane emissions. These actions may be contained in this code of practice or may be developed by the facility. Also record the date on which these actions were initiated at the paint stripping facility.
• It is also recommended to record the quantity of dichloromethane, as contained in paint strippers, used per year. Commercial paint strippers should ask the paint stripper manufacturer or their supplier to track the facility's annual paint stripper purchases as well as the dichloromethane content of that product. Running totals on invoices may be provided, indicating the total paint stripper and dichloromethane usage for the year to date.

Should the manufacturer or supplier be unable to provide a running total of annual dichloromethane consumption, this amount may be estimated. To determine the quantity of dichloromethane used per year, keep records on the quantity (volume) of dichloromethane-based paint stripper purchased per year and its percent dichloromethane content. Product information sheets for the paint stripper will contain a range of the dichloromethane content in the paint stripper (for example, 3-7%, 5-10%, 40-70%) or the actual content (for example, 80%). The percent dichloromethane content may be expressed on a weight basis or a volume basis. Use the actual or an estimated content level to calculate total dichloromethane consumption for the year.

For instance, 10 drums, each 205 litres, of dichloromethane-based paint stripper were purchased during the year. This gives 10 × 205 = 2050 litres of paint stripper purchased for the year. If the average dichloromethane content of the paint stripper is 70% by volume, 2050 litres × 0.70 = 1435 litres of dichloromethane were purchased during the year. If the average dichloromethane content of the paint stripper is 70% by weight, first convert the 2050 litres of paint stripper to mass using the density of the formulation (found on the Material Safety Data Sheet). Then multiply that mass by 0.70 to obtain the total mass of dichloromethane purchased for the year. To convert the mass of dichloromethane into volume, divide the mass (in kilograms) by the density of dichloromethane (1.32 kilograms per litre).

Record the quantities of dichloromethane-containing waste along with the details of the waste disposal and/or recycling company and method of disposal or recovery. Subtract this quantity from purchases to estimate releases.

If the ownership of a commercial paint stripping operation is transferred, it is recommended to transfer records related to paint stripper use and reduction measures implemented to the new owner along with a copy of this code.

2.8 Recommended training

• It is recommended to train individuals responsible for paint stripping to use the specific work practices contained in this code of practice. In addition to an initial training, give all operators an annual refresher course. The training provided should teach the skills necessary to implement the work practices in this code of practice.
• Train the individuals responsible for paint stripping to implement the recommended paint stripper application instructions provided by the manufacturer.
• Employers should ensure that employees are familiar with Material Safety Data Sheets, other health and safety documents, and any paint stripper product literature provided by suppliers. If the provided product literature does not enable the employer to accurately determine the quantity of dichloromethane in the paint stripper, the employer may wish to contact the supplier for a more precise concentration.
• Train all employees involved in the handling and use of paint strippers to use the appropriate personal protective and emergency equipment.