Code of Practice for reducing dichloromethane emissions from use of paint strippers: chapter 1

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

1.0 Code of practice for paint stripping activities at commercial furniture restoration facilities

1.1 Applicability

Part 1 of the code of practice applies to furniture restoration facilities that use:

• gel-based paint stripper that is brushed onto the furniture surface, and/or
• liquid-based paint stripper that is used in a flow-over system

Furniture restoration facilities may also use dip tanks to strip paint. However, this practice is not widespread. A discussion of work practices applicable to furniture restoration facilities that use dip tanks is provided in Part 2 of the code of practice (Section 2.2), which identifies work practices for metal parts paint strippers that use dip tanks.

Many of the work practices outlined below are designed to reduce the dichloromethane evaporation rate of the paint stripping formulation. Reducing the evaporation rate serves to reduce dichloromethane emissions. In addition, minimizing the evaporation rate and emissions will serve to reduce the amount of wasted paint stripper, thus reducing a facility's overall operating costs.

Not all work practices identified in this section are appropriate for every facility. Each furniture restoration facility should review the code and implement those work practices appropriate for its specific situation.

1.2 General recommended work practices

The work practices outlined in this section apply to furniture restoration facilities that use either gel- or liquid-based paint stripper.

1.2.1 Use methods other than paint stripping to restore furniture items

It is possible to avoid paint stripping entirely when restoring some furniture items. Some furniture can be simply sanded or washed to remove grease before refinishing. Other furniture items may be recoated without paint stripping or simply waxed and buffed. Applying lacquer thinner mixed with shellac over the existing coating is another option. For some furniture items, avoiding paint removal can minimize damage that can potentially occur during the restoration process and reduce the cost of the restoration project. The potential to avoid paint stripping will depend on customer requirements and the purpose of the restoration project.

1.2.2 Evaluate non-dichloromethane-based paint stripping alternatives

Alternatives to dichloromethane-based paint strippers may be available, but should be thoroughly evaluated before being employed. All possible benefits and drawbacks of each alternative (for example, relative toxicity) should be compared with those of using dichloromethane-based paint strippers before a decision is made.

1.2.3 Use manual stripping for easily removed coats of paint

Coats of paint that are easily removed should be first stripped from the furniture item manually using a scraper or sandpaper prior to applying the paint stripper. Stripping excess coats of paint with a scraper or sandpaper should reduce the quantity of paint stripper required to remove the remaining coats.

1.2.4 Use paint strippers with lower dichloromethane content when possible

Paint strippers used by furniture restoration facilities generally contain approximately 70-90% dichloromethane. Whenever possible, it is recommended to use paint strippers that have a lower dichloromethane content. (If the product literature does not provide enough information to determine the quantity of dichloromethane in the paint stripper, consider contacting the supplier for a more precise concentration.)

Paint strippers with lower dichloromethane content will not in all instances result in reduced dichloromethane emissions. Therefore, each facility should evaluate its own particular 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 furniture items 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.

1.2.5 Clean the furniture item prior to stripping

Materials caught in crevices may prevent the paint stripper from removing all of the paint from the furniture surface. Therefore, additional applications of paint stripper may be required in order to remove all of the paint completely. Cleaning furniture items will also help to avoid contaminating the paint stripper (that is, in a flow-over system), which reduces the product's effectiveness. Sanding can also be used to clean the furniture item and to break down the surface coating, allowing the paint stripper to more easily penetrate the coating.

1.2.6 Use paint strippers that contain a wax additive

The paint stripping formulations used should contain a wax additive that, once applied, will harden and form a barrier between the paint stripper and the surrounding air. This wax barrier reduces evaporation of dichloromethane from the paint stripper and should be left undisturbed until enough contact time between the surface and the paint stripper has elapsed.

1.2.7 Conduct paint stripping activities within the optimal temperature range whenever possible

Use paint stripper within the optimal temperature range, usually between 13°C and 18°C, whenever possible. Stripping paint in this temperature range allows for a rapid reaction time and minimizes evaporation and premature drying of the paint stripper. Applying paint stripper below 13°C may result in a slow rate of reaction between the dichloromethane and the coating. Dichloromethane may evaporate before the coatings have been stripped from the wood substrate. In addition, the wax barrier may solidify completely, thereby reducing the effectiveness of the paint stripper. Applying paint stripper at temperatures above 18°C may result in evaporation of the dichloromethane before it has reacted with the coatings. High temperatures also may inhibit the formation of the wax barrier.

Minimizing evaporation loss of dichloromethane by using the paint stripper at ambient temperatures of between 13°C and 18°C can both reduce the amount of paint stripper needed and decrease the time required for the paint stripper to act.

If working outdoors, it is recommended to apply paint stripper in cool, shaded areas. Applying paint stripper in direct sunlight should be avoided. The dichloromethane in the paint stripper may dry too quickly if the surface being stripped is heated or exposed to sunlight. An additional application of paint stripper may then be required. Paint strippers maintain their effectiveness on cool, shaded surfaces.

1.2.8 Test the surface before applying the paint stripper

Test the surface of the furniture item to determine the type of coating to be removed and to ensure that an appropriate paint stripping formulation is used. Commercial testing devices have been developed; these indicate whether the coating to be removed from the furniture item is nitrocellulose lacquer, polyurethane, or some other type of coating. These devices work by changing colour when they are applied to the furniture coating. A small section of the furniture item is usually tested. Applying alcohol or lacquer thinner to the furniture item can also indicate the type of coating that has to be removed and whether the paint stripper will be effective. For easily removable coating(s), low- or non-dichloromethane content paint strippers can be applied.

1.2.9 Cover surface areas coated with paint stripper

The use of a cover will reduce the amount of contact between the dichloromethane in the paint stripper and the surrounding air as well as allow a longer reaction time between the paint stripper and the coating. This will slow the dichloromethane evaporation rate and slow the drying of the paint stripper. As a result, using a cover may reduce the need for additional applications of paint stripper. Use wax paper, nylon, cellulose (paper)-based covers, or plastic sheeting (for example, polypropylene) that is chemically resistant to dichloromethane and other organic solvents. Test the reaction between the paint stripper and the selected cover prior to using it on the furniture items. Used covers should be properly disposed of, as dichloromethane will eventually diffuse through them.

This work practice may be more suitable for (i) furniture items with flat surfaces, such as tables, and (ii) coats that have proven difficult to remove and will require a long penetration time.

1.2.10 Optimize ventilation with consideration for worker exposure

It is important to ensure that there is adequate ventilation for workers using dichloromethane-based paint strippers; however, creating major air disturbances in the work area can increase solvent emissions by accelerating evaporation. Ensure that the amount of ventilation is sufficient, but not so excessive as to create major air disturbances.

1.3 Recommended work practices - hand stripping (gel-based paint stripper)

The work practices outlined in this section apply to furniture restoration facilities that use gel-based paint stripper. Gel-based paint strippers are typically applied manually with a brush.

1.3.1 Brush paint stripper onto the furniture surface in one direction, using as few strokes as possible

Paint strippers should not be applied to the furniture item using back and forth strokes, as this disturbs the wax seal that forms on the surface. When applying the paint stripper, minimize the number of strokes over the surface, since this also disturbs the wax seal. Disturbing the wax seal results in exposure of the dichloromethane in the paint stripper to the surrounding air, which increases the evaporation rate of the stripper. Excessive brushing will also result in the entrainment of air in the paint stripper, which reduces the contact between the dichloromethane and the surface area to be stripped. Excessive brushing will therefore reduce the effectiveness of the paint stripper and increase the solvent emissions.

1.3.2 Apply paint strippers to workable surface areas

Paint stripper should be applied in small, workable areas that will allow the paint to be scraped off before the paint stripper dries. The dichloromethane and other solvents in the paint stripper will eventually evaporate, causing the applied paint stripper to dry. Should this happen prior to removal of the paint surface, an additional application of paint stripper will be required. It may be more difficult to remove the paint once a coat of paint stripper has been left to dry on a piece of furniture. Stripping furniture in segments will prevent this from happening. The size of the workable area will depend on the experience of the individual applying the paint stripper.

Applying stripper using the manufacturer's recommended rate will minimize the number of instances of paint stripper drying prior to removal. Although the amount required will depend upon the item in question and how many coats must be removed, as a guide, each 3.8 litres (1 gallon) of paint stripper should be able to strip about 7-9 square metres (75-100 square feet) of surface.

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

Frequent testing of the furniture surface being stripped will disrupt the surface wax layer that forms to minimize dichloromethane emissions.

To reduce waste, ensure that the paint stripper has fully penetrated the paint before scraping it off. Paint stripper that is removed before it penetrates the paint may not fully remove all coats of paint, and another application of paint stripper may be required. Test the paint stripper to determine whether it has penetrated the paint and is ready to be removed. An indication that the paint stripper has penetrated the paint and is ready to be scraped off can vary, depending on the coat, but may include bubbling of the surface coat or flaking or sheeting of paint when tested. When testing the paint stripper, test only a small area and, as much as possible, try not to disturb the wax layer formed to minimize solvent emissions.

1.3.4 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 composition and properties as the 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.

1.3.5 Capture and reuse paint stripper where applicable

Stripping vertical furniture surfaces or surfaces that are close to the floor may cause paint stripper to drip onto the floor. If these drippings are caught on trays (for example, pie plates placed under the furniture legs), they can be reapplied to the surface being stripped. This will reduce the overall quantity of paint stripper used.

1.3.6 Use high-viscosity (thick) paint strippers

The use of high-viscosity paint strippers on vertical surfaces reduces drippings from the surface being stripped, such that additional applications of stripper may not be necessary. Liquid-based paint strippers should not be brushed onto vertical furniture surfaces, as the paint stripper will not form a film and will run off the surface before it can react with the coating.

1.3.7 Scrape layers of paint from the furniture starting at the top

When removing the paint stripper and coats of paint, always begin the scraping process at the top of the furniture item being stripped and proceed downward. Starting the scraping process at the top of the furniture item prevents the potential for recoating of previously stripped area with paint or paint stripper scrapings. This may reduce the amount of paint stripper used.

1.4 Recommended work practices - flow-over (liquid-based paint stripper)

The work practices outlined in this section apply to furniture restoration facilities that use liquid-based paint stripper, typically applied using a flow-over system. Consider equipping flow-over systems 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.

1.4.1 Strategically plan paint stripping activity

By strategically planning paint stripping activities, exposure of the paint stripper left in the flow-over tank (or the unsealed storage container) to the surrounding air can be minimized. Paint stripping activity can be scheduled so that all of the furniture items to be stripped for the day are dealt with sequentially (for example, in the morning). Therefore, the paint stripper contained in the flow-over tank storage container can be sealed after the last item has been stripped. If paint stripping activities occur throughout the day, paint stripper in the flow-over tank will be exposed to the atmosphere for an extended period of time, thus increasing the dichloromethane evaporation rate and emissions and potentially decreasing the efficiency of the paint stripper as its composition changes.

1.4.2 Collect paint chips entering the recirculating system in a strainer

If a pump is used to circulate paint stripper, collect the paint chips that flow through the drain in the flow-over tank and into the circulation system in a strainer. A strainer can catch the paint chips that flow through the flow-over tank drain. These paint chips can then be removed from the strainer. The dichloromethane should be allowed to drain separately into a paint can or similar collection device. The paint stripper that is captured in this system can then be recycled into the flow-over system. In certain circumstances, it may be possible to add a thin water layer to the collection device to minimize dichloromethane emissions.

1.4.3 Apply paint stripper close to the drain for the recirculating system

The furniture item that is placed in the flow-over tank should be located near the drain for the recirculating system. This should ensure that paint stripper poured over the furniture item has a minimum distance to travel to reach the drain and the recirculating system. This should reduce the length of time the paint stripper is exposed to the surrounding air and, consequently, will likely reduce dichloromethane emissions.

1.4.4 Introduce paint stripper into the flow-over tank by pouring it into the circulation system

When introducing paint stripper into the flow-over system, pour paint stripper into the container that captures the paint stripper draining out of the flow-over tank. A hose attached to this container draws paint stripper up to be poured over the furniture item being stripped. This process is designed to minimize disturbance to the paint stripper and its exposure to the surrounding air. If paint stripper were poured directly into the flow-over tank, then it would have greater exposure to the surrounding air. In addition, pouring paint stripper directly into the flow-over tank rather than the container would entail considerably more splashing.

1.4.5 Circulating pumps should be kept off when the flow-over system is not in use

Turn off pumps that circulate paint stripper in the flow-over system when the system is not in use. Turning circulation pumps off will stop the flow of the paint stripper and, therefore, halt exposure of the paint stripper to the surrounding air.

1.4.6 Keep the hose end close to the furniture item being stripped

Keeping the hose end close to the furniture item being stripped should reduce the distance that the paint stripper has to travel and therefore reduce its exposure to the surrounding air. The distance between the hose and the furniture item being stripped will depend on the item. For instance, the hose end may be held higher when stripping a table so as to disperse the paint stripper more efficiently.

1.4.7 Allow paint stripper to drain from the furniture in the flow-over tank before rinsing

Before removing furniture from the flow-over tank and taking it to the rinse area, let the furniture item drain completely (that is, the paint stripper has stopped dripping). In addition to rotating furniture above the flow-over tank, use a brush to help return excess paint stripper to the flow-over tank. Maximizing the amount of paint stripper returned to the flow-over tank should reduce the quantity lost in the rinsing area. This will also reduce the quantity of paint stripper required. The furniture items can be physically manipulated or brushed in order to assist in removing excess paint stripper. Flat surfaces such as a tabletop can be leaned against the side of the flow-over tank so that the paint stripper will drain back into the flow-over tank.

1.4.8 Apply recycled paint stripper to furniture items with numerous coats

Apply recycled paint stripper to furniture items that have several layers of coating in order to remove most of the paint. Then apply new paint stripper to remove the remaining paint. Using this process should reduce the amount of paint stripper contaminated with paint chips. Contamination of paint stripper with paint chips reduces its effectiveness. The first layers may be easier to remove, and therefore the lower-strength, contaminated paint stripper can be used. New paint stripper should be used on furniture items that have light coatings or that are nearly bare.

1.4.9 Use solvent recovery companies or in-house recycling technology

Paint chips and sludge can be drained at the furniture restoration facility to recycle paint stripper, or the paint chips/sludge can be sent to the solvent recycling company at various stages of the recycling process. For instance, the paint chips/sludge can be sent to the recycler immediately after capture, or they can be sent after the furniture restoration facility has collected as much of the paint stripper as possible. The furniture restoration facility can determine at which stage it would be in its best interest to send the paint chips/sludge to a solvent recycler.

Solvent recovery technology is available to extract dichloromethane contained in paint chips removed from furniture at restoration facilities. These solvent recovery systems are generally used only after the collected paint chips have been put through the recycling system at the furniture restoration facility. That recycling system usually consists of allowing paint stripper to drain by gravity from the collected paint chips. The paint chips are then introduced into the solvent recovery system to capture the remaining dichloromethane. The benefits and potential drawbacks of using solvent recovery technology should be fully evaluated prior to making a decision about its use at each furniture restoration facility.

1.4.10 Ensure that the paint stripper does not dry on the furniture item being stripped

Do not allow paint stripper to dry on the surface of the furniture item being stripped. Scrape all paint off the furniture item when the paint stripper coating is wet. The dichloromethane and other solvents in the paint stripper will eventually evaporate, causing 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, resulting in more emissions.

1.4.11 Drain paint stripper from the flow-over tank when the tank is not in use

Draining paint stripper from the flow-over tank and storing it in a sealed container will reduce contact between the paint stripper and the surrounding air. This work practice should result in less dichloromethane evaporation than simply covering the flow-over tank when the system is not in use. However, covers may be more practical when paint stripping activities have ceased for only a short period of time (for example, lunch break).

1.4.12 Cover the flow-over tank when not in use

For those furniture restoration facilities that do not use a circulating system, a tight-fitting cover should be placed on top of the flow-over tank at all times, except when the system is in use. This cover will reduce contact between the paint stripper and the surrounding air, and should minimize the evaporation of dichloromethane.

1.4.13 Reduce the surface area of the flow-over tank

Flow-over tanks come in various sizes (height, width, length). Using a deeper flow-over tank that is shorter and narrower will reduce the surface area of the exposed paint stripper in the flow-over tank. Minimizing surface area should reduce the amount of paint stripper in contact with the surrounding air, and should reduce emissions.

1.5 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.

• 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.

1.6 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 to the residues in the container.
• 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, or provincial 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.

1.7 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 either 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 value given 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.

1.8 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 period, 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.
• Consider enrolling in a paint stripping course (for example, Fanshawe College in Ontario currently offers an eight-week course on furniture refinishing).
• Train all employees involved in the handling and use of paint strippers to use the appropriate personal protective and emergency equipment.