Emission of Volatile Organic Compounds from Wood and Wood-Based Materials

6. Evaluation of Product Modification/- Substitution

6.1 Wood and Wood-Based Products in a Wide Environmental Perspective
6.2 Indoor Environment Aspects
6.3 Evaluation Examples for Wood-Based Building Materials, Furniture and Interior Furnishings
6.3.1 Floor Example
6.3.2 Wardrobe Example
6.3.3 Coffee Table Example
6.3.4 Bookcase System Example
6.3.5 Office Table Example
6.3.6 Cottage Example
6.3.7 Evaluation Model in Principle

In cases where the indoor air is given a high priority, it should be recommended to choose lower-emitting materials and products in order to reduce the emissions from materials and products and to obtain a larger probability of reducing effects and possible health effects in consequence of the emission from these materials and products.

If lower-emitting materials and products are aimed at, the modification/ substitution of materials and products can be carried out according to the evaluation model shown in principle in Figure 4.1. Modification/substitution is recommended, when the emission contains toxicologically unknown, chemical substances and chemical substances with carcinogenic, reprotoxic or immunologic effects.

The modification of materials and products should be considered for materials and products with a relatively high S-value and a high indoor-relevant time-value.

The following substitution considerations, which only constitutes a minor part of this project, comprise only other effects and aspects (in excess of the significance for the air quality), to the extent that these are generally known.

Examples of potential modifications and substitutions were considered in a broad environmental perspective including the good indoor environment and taking the technical performance hereunder functional class and economical aspects into account. The examples imply usual application of the wood-based materials and products

6.1 Wood and Wood-Based Products in a Wide Environmental Perspective

The afforestation has a major positive environmental effect.

Wood is a renewable resource, as long as continuous transplanting of new trees corresponds to the felling. The duty to preserve the forests implies that the forest after the felling should be re-established by transplanting and tending in order to create sustainable forestry. (Ministry of the Environment and Energy, 1995).

Waste wood can in excess of being used in wood-based panels a.o. be used as fuel and return approx. 30-50% of the total energy content. Wood treated with chemicals can not in all cases be burned under simple conditions, as it may lead to emissions of environmentally hazardous substances. It could, however, be burned under controlled conditions at a diffuse disposal plant.

During the combustion more energy is released than was used for manufacture of most "simple" wood products e.g. glulam beams. The solid residues, ashes, will contain different minerals and possibly residue of chemicals and possibly heavy metals, which were used by manufacture of the product. Such ashes should be deposited in a controlled way. The ashes from pure wood could be used in the agriculture or the forestry. (Evald, A., 1993).

By deposit the wood is deteriorating by the presence of adequate oxygen to carbon dioxide and water. The different additives applied to the wood, will be deteriorated at different rates depending on the biological accessibility. (Evald, A., 1993).

The largest safety and health problems by processing wood is dust, noise and ergonomics. The extent of a wood dust problem is depending on the size of the particles and wood species. Exposure to wood dust can lead to serious occupational related diseases (Jensen, L.D., 1987). In Denmark there is a threshold limit value for total wood dust in the work environment, according to the threshold limit value list of the Danish Working Environment Service. The dust causes besides mechanical irritation of eyes, mucous membranes or the skin, chemical irritation and sensitizing. Asthma and dermatitis are the most frequent work environmental problem of the wood industry. The workers of the furniture industry bear a larger risk of nasal tumours. Different types of cancer are continuous to be caused by exposure to wood dust. (WHO, 1987). There can be several reasons for this carcinogenic reaction, such as continued mechanical mucous irritation, influence from fungi, wood borne fungi or metabolic products from these or chemical substances used by manufacture of wood (Danish Environmental Protection Agency, 1988).

Seen in a broad environmental perspective the documentation on materials and products manufactured for interior use generally should include indoor air considerations and other aspects of essential significance for the product in the indoor air hereunder e.g. environmental impact in connection with cleaning and maintenance. For building products and interior furnishings the the actual lifetimes is often essential to determine whether the products are environmentally friendly or not.

6.2 Indoor Environment Aspects

Indoor environment is a combination of all climatic factors influencing the stay and comfort of humans indoors.

The term indoor environment means mainly (SBI, 1995, modified):

	Balance between fresh-air intake and source strength
	Thermal conditions described by room temperature, air velocity, relative humidity, air exchange, draft etc.
	The air quality is described by the content of pollution such as dust, gases and vapours and thereby connected odours
	Microbiological pollution
	Static electricity described by charging of persons
	Light conditions described by light strength, colour, contrasts and reflexes
	Acoustics described by sound intensity and frequency distribution
	Ionizing radiation described by radon concentration

In principle a good indoor environment should be aimed at, as we spend the main part of our lives indoors. Some people spend all their time indoors.

Gases and Vapours

Exposure to gases and vapours can lead to a number of symptoms and diseases. The most frequent symptoms are mucous membrane irritation in eyes, nose and throat as well as dermatitis. Furthermore, fatigue , indisposition, headache and sense of heaviness in the head. Such symptoms often do not point at a specific disease, but could be ascribed to bad indoor environment. When a large number of persons show the same symptoms it is described the "sick building syndrome". It should be noted that some persons are more sensitive than other towards e.g. air pollution.

Building materials, furniture and interior furnishings can have a large influence on the indoor air, e.g. because many different organic substances are emitted to the indoor air.

A number of examples exist in which materials hereunder former generations of particleboards and lacquered wood surfaces caused indoor air problems. Emission of formaldehyde from particleboards glued with urea-formaldehyde glue is among the most notorious. Irritation in eyes, headache and pricking odour are symptoms perceived by exposure to formaldehyde over a certain concentration. For UV-lacquers emission of certain photoinitiators and their deterioration products are known to a have an unpleasant odour (Salthammer, T., 1996).

6.3 Evaluation Examples for Wood-Based Building Materials, Furniture and Interior Furnishings

The examples stated below are based on the wood and wood-based materials, which were investigated by emission chamber measurement. As the investigated materials can not be considered as representatives of all variables of the investigated material types, further commonly known material experiences have been included in the modification and substitution proposals.

The considerations concerning modification and substitution have been carried out without regard to concrete conditions and implies ideal conditions as well as "everything else alike" considerations. As a part of more detailed modification and substitution considerations actual conditions should be taken into account, which might influence technical, environmental or economical aspects.

The following examples comprise comparison of variables of typical furniture products, types of interior furnishings and building materials. The product

examples, which have been made with a theme for inspiration by modification/substitution considerations, primarily illustrate conditions of importance for the impact of the materials on the indoor environment. Further conditions could be included, where these have a decisive influence on the modification/substitution, and their consequences have been described and generally accepted. Description of a product in relation to a given application as well as general and specific comments elaborate the considerations.

Examples of conditions, which have been considered in connection with modification/substitution are given in the following:

Indoor Environment

Work Environment

Exterior Environment

•   Possible limitations in consequence of the modification/substitution

Economy

The economic considerations have been made primarily in relation to the necessary technical basis for modification/substitution. It should be stressed that the stated modifications/substitutions are only examples. The evaluation examples are thus not synonymous with necessity of implementation of the modification/substitution.

Model for Evaluation

In the efforts to increase the clearness a proposal for a model for evaluation has furthermore been given. The proposed model makes an evaluation of the original product compared with the modification/substitution possible.

The evaluation model in principle is illustrated for the evaluation example "floor - lacquers and oils for treatment of wood floors" what regards indoor environment (function and indoor air).

Evaluation of relevant properties is based on the following classes:

	Among the best material
	Among acceptable materials
	Among the poorest materials/least acceptable materials

Such a schematic version implies in the nature of the case risks of generalization and simplification of the problems in relation to practice.

Wood floor treated with lacquer and oil.

Theme: "Different materials"

Wood floors treated with water-borne lacquer, polyurethane lacquer, acid-curing lacquer or oil treatment (oil/alkyd basis) or pre-coated floor with UV-curing lacquer

Wardrobe

Wardrobe of veneered particleboard with transparent lacquer

Theme: "formaldehyde emission"

Wardrobes of veneered urea-formaldehyde glued particleboards coated with acid-curing lacquer or of veneered polyurethane glued particleboards with UV-curing lacquer. Wardrobes in a bedroom can e.g. have a wardrobe front area of 0.2 m²/m³ and a surface area of other surfaces in contact with the indoor air of approx. 0.8 m²/m³.

Coffee Table

Coffee table of uncoated solid wood and veneered particleboard with transparent lacquer respectively.

Theme: "Low material load"

Coffee tables of solid ash, beech, oak or pine or veneered ureaformaldehyde glued particleboard coated with water-borne lacquer, acid-curing lacquer or polyurethane lacquer. The surface of the coffee table constitutes usually a relatively small part of the surface area in the standard room, e.g. 0.12 m²/m³.

Bookcase system

Bookcase system of uncoated solid wood and veneered particleboard coated with transparent lacquer.

Theme: "High material load"

Bookcase system of solid beech, oak or pine and veneered particleboard coated with water-borne lacquer, nitrocellulose lacquer or UV-curing lacquer. The surface of the bookcase system constitutes usually a relatively large part of the surface area of the standard room often more than 2.2 m²/m³.

Office Table

Office table of veneered particleboard with different types of transparent lacquer.

Theme: "Material combinations"

Office tables of urea-formaldehyde-glued particleboard coated with polyurethane lacquer, acid-curing lacquer, water-borne lacquer or UV-curing lacquer.

Cottage

Cottage of pine.

Theme: "Deviation from common use"

A cottage covered with uncoated pine on floor, ceiling and all 4 walls.

6.3.1 Floor Example

Wood floor coated with lacquer and oil.

Theme

Different materials.

Product Description

Wood floors coated with water-borne lacquer, polyurethane lacquer, acid-curing lacquer or oil treatment (oil/alkyd basis) or pre-coated floor with UV-curing lacquer.

Function

When choosing a flooring it is essential to include the application and thereby the performance class, as the choice should be adjusted to the need hereunder the technical properties, cleaning and maintenance.

Performance wise water-borne lacquer, 2-component polyurethane lacquer and 1- or 2-component acid-curing lacquer as well as pre-coated UV-curing lacquer are at the same level. Polyurethane, acid-curing or pre-coated UV-curing lacquer with an extra coat is usually recommended when a larger resistance to wear is required.

For the oil treatments the performance properties vary dependent on type of oil (and "generation" of oil). In practice the term "oils" is used for products spanning from wax treatments (with non-drying binder) to oils and alkyds to traditional lacquer treatments. Division of products with drying binders in oils and alkyds are used, as these can have very different film formation resulting in different properties.

Generally, oil treatments give a poorer pore density, poorer resistance towards liquids and poorer resistance to wear than alkyds. Oil consumption depends furthermore on type of oil, on e.g. walking load on the floor (and the resulting need for maintenance and renovation of the oil treatment) and on the oil penetration of the wood floor, which again depends on e.g. wood species, moisture content and age.

The maintenance frequency is larger for oils and lacquers. A maintenance interval between the oil treatments varies typically between 2-12 months, while re-coating typically is performed with intervals of 3-15 years. Aesthetic regards are often significant for choice of oil treatments in stead of lacquers.

Indoor Air

For the oil treatments the indoor air properties vary dependent on oil type (and "generation" of oil) etc. Oils and alkyds with drying binder contain usually aliphatic or aromatic hydrocarbons, which can be more or less volatile. Heavily evaporating solvents influence everything else alike the indoor air in a relatively larger time perspective than the more volatile.

From the oils emission is primary seen, which can be traced back to volatile organic compounds in the oils and alkyds, which are formed during drying. From the investigated acid-curing lacquer, especially, a considerable formaldehyde emission is seen. In the emission from the investigated UV-curing lacquer and polyurethane lacquer no monomers nor unreacted nor partly reacted pre-polymers have been identified. Isocyanates react fast with the humidity of the air. From UV-lacquers certain photo initiators and their deterioration products are known to have an unpleasant odour.

Other conditions of essential importance for the emission comprise: Oil absorption in the wood floor and need for re-treatment. The higher oil absorption and higher interval between re-treatment (maintenance and renovation) the higher emission.

Nothing suggests that it is essential whether the oil treatments are of a natural origin or synthetically produced. Allergic reactions have been seen in connection with odour substances added to the oils. The odour substances have otherwise no special effect on the product.

Work Environment

Safety and health information on lacquers and oils is available in the code number according to the regulations of the Danish Working Environment Service. The digit before the hyphen informs which precautionary measures to take against inhalation of volatile substances. (00-is the lowest and 5- the highest). The digit after the hyphen informs which personal protective equipment to be used to protect against:

	Contact with skin and eyes
	Inhalation of dust
	Consumption of the product

The investigated oils and lacquers have the following code number in a ready-to-use mixture and the following content of organic solvents (%VOC) respectively.

Table 6.1

Lacquers and oils, floors

Special training is required in connection with use of polyurethane lacquers.

By application and handling of UV-curing lacquers there is a risk of immunologic reaction from not totally cured specimens and also a risk of exposure to UV-radiation.

Possible wood or grinding dust is a problem when handling all these materials. Grinding dust from grinding of UV-curing lacquer and especially from the inter-grinding of UV-primer can contain unreacted monomers and other reactive substances.

Exterior Environment

Solvents in oils and lacquers are emitted to the environment, in case they have not been regained or burned.

The investigated polyurethane lacquer and acid-curing lacquer contain approx. 60% VOC, oil on urethanealkyd- and linseed-oil basis contains approx. 50% VOC, and the water-borne lacquer and the UV-curing lacquer approx. 1.5% VOC.

Economy

Pre-coated floor with UV-curing lacquer has larger requirements to application facilities than the physical-chemical drying lacquers and oils.

If a change to UV-curing lacquer is considered, the costs in connection with change of the coating process and investment in new facilities as well as mea-sures to protect the work environment what regards the safety & health should be taken into account.

Modification/Substitution

The stated oils and lacquers will usually be able to substitute each other.

From material emissions alone the acid-curing lacquer could advantageously be substituted by the far less emitting UV-curing lacquer.

Specific Comments

In case additives or accessories have been used for assembly of the floor, which might cause emission e.g. glue for joint of groove and tongue, these should be included in the emission measurement and evaluation.

The investigated acid-curing lacquer is not representative for all acid-curing lacquers, according to experience today acid-curing lacquers are available which cause considerably less emission of formaldehyde.

Renovation of pre-coated floors with UV-curing lacquer requires grinding of the UV-curing lacquer and re-treatment with a new type of lacquer, as UV-curing can not be carried out in buildings. Coating with UV-curing lacquer will usually be limited to 2-dimensional specimens.

Oil treatment with some types of oil a.o. types containing heavy volatile paraffins require use of machines for polishing the wood surface after application of the oil.

In connection with re-coating with polyurethane lacquers it is a prohibited to spray apply outside spray booths and cabins.

Water-borne lacquers are often inapplicable on dark (and dark stained) wood species, as the lacquer changes appearance and appear as a film on the surface.

6.3.2 Wardrobe Example

Wardrobe of veneered particleboard with transparent lacquer.

Theme

Formaldehyde emission.

Product Description

Wardrobes of veneered urea-formaldehyde glued particleboards coated with acid-curing lacquer or of veneered polyurethane glued particleboards coated with UV-curing lacquer.

Function

When selecting materials it is essential to consider the performance requirements, hereunder how high requirement should be placed to the strength of surface and panel. The materials should furthermore be adjusted to application indoors.

Performance wise wardrobes are made of veneered urea-formaldehyde glued particleboards with acid-curing lacquer and wardrobes of veneered polyurethane glued particleboards with UV-curing lacquer at the same level.

The maintenance frequency and the technical lifetime of the wardrobes are likewise expected at the same level. The technical lifetime of the surfaces typically exceeds the actual lifetimes of the wardrobes.

Indoor Air

A wardrobe made of particleboards glued with urea-formaldehyde glue and with front and maybe body coated with acid-curing lacquer is an example of a product which might cause a considerable emission of primary formaldehyde (above threshold value for the indoor air).

From wardrobes coated with UV-curing lacquers volatile substances are seen reflecting the substances in the materials and the deterioration products from these. The emission can vary considerably from one UV-curing system to another. The emission from the UV-curing lacquer investigated in this project is very limited.

Emissions from uncoated wood-based panels are predominantly aldehydes and vary dependent on applied type of glue.

Other conditions of significance for the emission comprise: area of unsealed panel edges and number of open shelf bracket holes in the wood panels. The more open edges and holes the larger emission.

By sealing of the edges, minor structural changes of the wardrobe design e.g. by use of lists and by use of plugs to close the excessive shelf bracket holes, the emission can be reduced considerably.

Larger emissions are to be expected from wardrobes delivered directly from the production and only a few days after coating without total curing of the surface than from wardrobes stored unpacked or in perforated packing in a period

before installation at the end-user.

Work Environment

Health & safety information on lacquers is available in the code number according to the regulations of the Danish Working Environment Service. The digit before the hyphen informs which precautionary measures to take against inhalation of volatile substances. (00-is the lowest and 5- the highest). The digit after the hyphen informs which personal protective equipment to be used to protect against:

	Contact with skin and eyes
	Inhalation of dust
	Consumption of the product

The investigated lacquers have the following code number in a ready-to-use mixture and the following content of organic solvents (%VOC) respectively.

Table 6.2

Lacquers, wardrobes

For manufacture of polyurethane glued panels closed production systems are used. (At the moment none such panels are produced in Denmark). In Denmark special training is required in connection with use of polyurethane products. Working environmentally it is not favourable to substitute urea-formaldehyde-glue with polyurethane glue.

By application and handling of UV-curing lacquers there is a risk of immunologic reaction from not totally cured specimens and also a risk of exposure to UV-radiation.

Possible wood or grinding dust is a problem when handling all these materials. Grinding dust of UV-curing lacquer and especially from the grinding of UV-primer may contain unreacted monomers and other reactive substances.

Exterior Environment

Solvents in glues and lacquers are emitted to the environment in case they have not been regained or burned.

The investigated acid-curing lacquer contains approx. 60% VOC and the UV-curing lacquer approx. 1.5% VOC.

Economy

The polyurethane glued particleboards are more expensive to produce than urea-formaldehyde glued particleboards.

If a change to UV-curing lacquer is considered, the costs in connection with the change of the coating process and investment in new facilities as well as mea-sures to protect the work environment should be taken into account.

Modification/substitution

The stated lacquers and wood-based panels can usually substitute each other, even though polyurethane glued particleboards are more expensive than urea-formaldehyde glued particleboards.

Less hazardous glue types will have less impact on the working environment on the indoor air. At present, however, there are no alternative glues to gluing of wood-based panels keeping the same, good technical properties as urea-formaldehyde glue and polyurethane glue respectively. Notoriously, e.g. polyvinyl acetate-glue, which primary is used for edge gluing and veneering, has a poorer strength and "cracks" in the surface layer due to low creep resistance. Existing wood-based panels have been optimised according to technical properties. An indoor air adjustment by reduction of emissions from the wood-based panels will result in panels with a relatively lower strength.

From material emissions alone the acid-curing lacquer could advantageously be substituted with the far less emitting UV-curing lacquer.

Specific Comments

Wood-based panels are rarely used without surface coating. The investigated acid-curing lacquer is not representative for all acid-curing lacquers, noto-riously, today there are acid-curing lacquers giving cause to essentially lower formaldehyde emission.

Emission of photo initiators and their deterioration products are known to have an unpleasant odour. Non-reacted or partly reacted pre-polymers are known to cause allergy.

Coating with UV-curing lacquer will usually be limited to 2-dimensional specimens.

6.3.3 Coffee Table Example

Coffee table of uncoated solid wood and veneered particleboard with trans- parent lacquer respectively.

Theme

Low material load.

Product Description

Coffee tables of solid ash, beech, oak or pine or veneered unreacted formaldehyde glued particleboard coated with water-borne lacquer, acid-curing lacquer or polyurethane lacquer respectively.

The surface of a coffee table constitutes a relatively small share of the surface area in the standard room e.g. 0.12 m² surface/m³ room air. Regarding a larger material load please refer to the bookcase system example below.

Function

When choosing materials it is essential to consider performance requirements corresponding to e.g. the requirements to furniture from Danish Varefakta, The Danish Institute for Informative Labelling, including e.g. the resistance of the surface towards liquids etc. and thereby the cleanability of the surface.

Tables coated with acid-curing lacquer and polyurethane lacquer have generally more resistance towards liquids and heat and are more resistant to dirt than uncoated wood surfaces and tables coated with a water-borne lacquer. Often solid table tops are treated with soap or oil. For applications with a relatively large wear requirements, lacquered surfaces with acid-curing lacquer or polyurethane lacquer are usually recommended.

The technical lifetime of the tables is typically expected to be more than 10 years. Maintenance interval between soap and oil treatments vary typically between 1-4 times yearly, while re-coating with water-borne lacquer is carried out after 1-5 years and re-coating with acid-curing or polyurethane lacquer after 5-15 years.

Aesthetic regards are often of significance for choice of untreated, oil treated or surface leach/soap treatment in stead of lacquer.

Indoor Air

Seen from an emission point of view untreated, solid ash, beech, oak and surfaces with UV-curing lacquer are at the same level, while the emissions from uncoated, solid pine are considerably larger, mainly of terpenes.

From the tested veneered particleboard with water-borne acrylic lacquer an emission of alcohols and acetates is seen. From the surface coated with poly-urethane lacquer an emission of hydrocarbons and acetates is seen.

The emission from a coffee table constituting a relatively small surface (0.12 m²/m³) and composed of the above materials will usually result in a minor and negligible impact on the indoor air.

Work Environment

Health & safety information on lacquers is available in the code number according to the regulations of the Danish Working Environment Service. The digit before the hyphen informs which precautionary measures to take against inhalation of volatile substances. (00-is the lowest and 5- the highest). The digit after the hyphen informs which personal protective equipment to be used to protect against:

	Contact with skin and eyes
	Inhalation of dust
	Consumption of the product

The investigated lacquers have the following code number in a ready-to-use mixture and the following content of organic solvents (%VOC) respectively.

Table 6.3

Lacquers, coffee table

Special training is required in connection with use of polyurethane lacquers.

Possible wood or grinding dust is a problem when handling all these materials.

Exterior Environment

Solvents in lacquers are emitted to the environment in case they have not been regained or burned.

The investigated polyurethane and acid-curing lacquer contain approx. 60% VOC and the water-borne lacquer approx. 1.5% VOC.

Economy

Tables made of solid wood are relatively more expensive than tables of veneered particleboard, in return solid tables are more durable in consequence of the possibility of re-treatment by means of grinding.

Modification/Substitution

The stated treatments will apart from the water-borne lacquer usually substitute each other.

Specific Comments

Furniture of solid wood is traditionally considered more genuine than veneered products.

Notoriously, untreated surfaces and surfaces treated with wax, oil, or soap are performance wise good alternatives to lacquered surfaces under the condition that they only are used on the most exposed surfaces (e.g. upperside of the table top) when these table parts are made of solid wood and that they are maintained properly. Surface leach/soap treatments were not included in this project.

Regarding type of oil and composition reference is made to the previous floor example.

The investigated acid-curing lacquer is not representative for all acid-curing lacquers, today acid-curing lacquers are available, which causes considerably less emission of formaldehyde.

The investigated water-borne lacquer is not representative for all water-borne lacquers, it should be expected that other water-borne lacquers are available emitting less.

Water-borne lacquers are often inapplicable on dark (and dark stained) wood species, as the lacquer changes appearance and appear as a film on the surface.

6.3.4 Bookcase System Example

Bookcase systems made of untreated, solid wood and veneered particleboard coated with transparent lacquer respectively.

Theme

High material load.

Product Description

Bookcase systems of solid beech, oak or pine or veneered urea-formaldehyde glued particleboard coated with nitrocellulose lacquer, water-borne lacquer or UV-curing lacquer respectively

The surface of a bookcase system has a relatively large share of the surface area in the standard room e.g. 2.2 m² surface/m³ room air. (The coffee table example comprises application of materials with a smaller material load).

Function

When selecting materials it is essential to consider performance requirements corresponding to e.g. the requirements to furniture from Danish Varefakta, Danish Institute for Informative Labelling, including e.g. the resistance of the surface.

Performance wise bookcase systems coated with UV-curing lacquer are gene-rally more resistant and are more resistant to wear and dirt than water-borne lacquer, nitrocellulose lacquer and uncoated wood surfaces. For applications with a relatively large requirements to wear lacquered surfaces are usually recommended.

Curing of the water-borne lacquer takes longer time than curing of lacquers with a larger solvent content.

Indoor Air

Seen from an emission point of view untreated, solid beech, oak and veneered particleboard coated with UV-curing lacquer are at the same level, while the emissions from uncoated, solid pine are considerably larger, mainly of terpenes. From the tested veneered particleboard with nitrocellulose lacquer and water-borne acrylic lacquer respectively an emission of alcohols and acetates is seen.

The water-borne lacquer results in an emission relatively longer, as the solvents evaporate slower than the solvents in the nitrocellulose lacquer.

The emissions from a bookcase system constituting a relatively large surface area (2.2 m²/m³) could influence the indoor air considerably.

Work Environment

Health & safety information on lacquers is available in the code number according to the regulations of the Danish Working Environment Service. The digit before the hyphen informs which precautionary measures to take against inhalation of volatile substances. (00-is the lowest and 5- the highest) statement. The digit after the hyphen informs which personal protective equipment to be used to protect against:

	Contact with skin and eyes
	Inhalation of dust
	Consumption of the product

The investigated lacquers have the following code number in a ready-to-use mixture and the following content of organic solvents (%VOC) respectively.

Table 6.4

Lacquers, Bookcase System

Regarding UV-curing lacquers there is risk of allergy by application and handling of not totally cured specimens as well as risk of exposure to UV-radiation.

Possible wood or grinding dust is a problem when handling all these materials. Grinding dust from UV-curing lacquer and especially the grinding of UV-primer may contain unreacted monomers and other reactive substances.

Exterior Environment

Solvents in lacquers are emitted to the environment in case they have not been regained or burned.

The investigated nitrocellulose lacquer contains approx. 80% VOC. Both the water-borne and the UV-curing lacquer have a low content of organic solvents (approx. 1.5%).

Economy

Furniture made of solid wood is relatively more expensive than furniture made of veneered particleboard.

Application of UV-curing lacquer has more extensive requirements to paint equipment than physical drying lacquers.

If a change to UV-curing lacquer is considered, the costs in connection with change of the coating process and investment in new facilities as well as measures to protect the work environment should be taken into account.

Modification/Substitution

The stated treatments will usually substitute each other, even though the environmental impact is considerably larger from nitrocellulose lacquer with a high content of highly volatile solvents.

On basis of material emissions alone untreated pine could advantageously be substituted by less emitting solid beech and oak or veneered particleboard with UV-curing lacquer or water-borne lacquer.

Specific Comments

Furniture of solid wood is traditionally considered more genuine than veneered products.

Nitrocellulose lacquer has in the 1990s again found use within the furniture industry as a result of some large-scale purchasers giving "formaldehyde-free" furniture a high priority and thereby departing from acid-curing lacquer. The acid-curing lacquer was substituted by nitrocellulose, when it was chosen not to change the classification according to some technical criterions.

The investigated water-borne lacquer is not representative for all water-borne lacquers, it should be expected that other water-borne lacquers are available emitting less.

Water-borne lacquers are often inapplicable on dark (and dark stained) wood species, as the lacquer changes appearance and appear as a film on the surface.

6.3.5 Office Table Example

Office table made of veneered particleboard coated with different types of transparent lacquer.

Theme

Material combinations

Product Description

Office tables of urea-formaldehyde glued particleboard coated with polyurethane lacquer, acid-curing lacquer, water-borne lacquer or UV-curing lacquer respectively.

Function

When selecting materials it is essential to consider performance requirements corresponding to e.g. the requirements to furniture from Danish Varefakta, Danish Institute for informative Labelling, including e.g. the resistance of the surface.

Performance wise polyurethane lacquers, acid-curing lacquers and UV-curing lacquer are at the same level. Generally, surfaces coated with water-borne lacquer are not so resistant as other types of lacquered surfaces. For applications with a relatively large requirements to resistance to wear, coating of the above types is recommended, but with an extra coat.

The technical life times and actual life times are generally larger than approx. 10 years.

Indoor Air

Emissions from veneered particleboard with UV-curing lacquer is considerably smaller than the emissions from veneered particleboard coated with polyurethane lacquer, acid-curing lacquer and water-borne lacquer respectively.

From the tested veneered particleboard coated with water-borne acrylic lacquer an emission of alcohols and acetates is seen - from the specimen coated with polyurethane lacquer an emission of hydrocarbons and acetates is seen and from the specimen coated with acid-curing lacquer a considerable formaldehyde emission is seen.

Work Environment

Health & safety information on lacquers is available in the code number according to the regulations of the Danish Working Environment Service. The digit before the hyphen informs which precautionary measures to take against inhalation of volatile substances. (00-is the lowest and 5- the highest). The digit after the hyphen informs which personal protective equipment to be used to protect against:

	Contact with skin and eyes
	Inhalation of dust
	Consumption of the product

The investigated lacquers have the following code number in a ready-to-use mixture and the following content of organic solvents (%VOC) respectively.

Table 6.5

Lacquers, Office Table

Regarding UV-curing lacquers there is risk of allergy by application and handling of not totally cured specimens as well as risk of exposure to UV-radiation.

Possible wood or grinding dust is a problem when handling all these materials. Grinding dust from UV-curing lacquer and especially the grinding of UV-primer may contain unreacted monomers and other reactive substances.

Exterior Environment

Solvents in lacquers are emitted to the environment in case they have not been regained or burned.

The investigated polyurethane lacquer and the acid-curing lacquer contain approx. 60% VOC, the water-borne and UV-curing lacquer approx. 1.5% VOC.

Coating of table legs and other parts is generally applied with a low utilisation of the lacquer. For such parts lacquers with a relatively low solvent content should be preferred.

Economy

Use of UV-curing lacquer has more extensive requirements to paint equipment than physical drying lacquers.

If a change to UV-curing lacquer is considered, the costs in connection with change of the coating process and investment in new facilities as well as

measures to protect the work environment should be taken into account.

Modification/Substitution

The stated lacquers apart from the water-borne lacquer will usually substitute each other.

By application of polyurethane lacquer, acid-curing lacquer or UV-curing lacquer on the table top and water-borne lacquer on the legs (and maybe on other surfaces with less impact on the environment with low lacquer utilisation by application), a technically as well as environmentally appropriate product is obtained.

On basis of material emissions alone the relatively low emitting UV-curing lacquer is preferred.

Specific Comments

From UV-lacquers emission of certain photo initiators and their deterioration products are known to have an unpleasant odour. Coating with UV-curing lacquer will generally be limited to 2-dimensional specimens.

The investigated acid-curing lacquer is not representative for all acid-curing lacquers, today acid-curing lacquers are available, which causes considerably less emission of formaldehyde.

The investigated water-borne lacquer is not representative for all water-borne lacquers. It should be expected that other water-borne lacquers are available emitting less.

Water-borne lacquers are often inapplicable on dark (and dark stained) wood species, as the lacquer changes appearance and appear as a film on the surface.

6.3.6 Cottage Example

Cottage of pine.

Deviation from common use.

A cottage with terpene-rich uncoated pine on floors, ceiling and all 4 walls.

The wall, ceiling and floor surfaces should be treated depending on the use of the cottage.

Emissions from untreated solid pine contain considerable amounts of terpenes, primary a -Pinene and 3 carene. The terpenes are the substances to give pine the characteristic odour.

Other properties of essential importance for the emissions comprise a.o. the age, drying and storage conditions of the wood. Fresher wood, shorter time of storage and lower drying temperature will everything else alike result in a larger emission.

In a relatively small cottage with a relatively large wood surface to a minor room air volume the indoor-relevant concentration could be considerable. The concentrations in the indoor air will be further extended, if the cottage for some reason was made relatively airtight resulting in a low air change.

Wood and grinding dust is a problem when handling pine.

The pine has a positive environmental impact cf. clause 6.1.

Isolation of the cottage to save energy could be a nuisance to the indoor air.

In principle it will be possible to limit the emission considerably by choosing a pine variable with a relatively low content of terpenes. The possibility of selecting such a pine quality will, however, in practice require increased attention and efforts at all levels in the chain from sawmill to end-user. This effort could desirably also include process and storage conditions to get the potential emissions emitted that can be a nuisance to the indoor air, but not a problem as emission to the working environment or the exterior environment before the products reach the end-users.

From material emissions alone the extra-ordinarily isolated cottage of uncoated pine for all-year use e.g. permanent habitation or forest kindergartens could advantageously be modified. Modification could consist of coating of the walls, floor, and ceilings with a relatively low emitting lacquer or paint, and/or measures securing a relatively large air exchange.

The pine odour is often considered a pleasant odour.

6.3.7 Evaluation Model in Principle

An evaluation model for relative description of materials of same type has been illustrated in Table 6.6 for the evaluation example "wood floor - coated with different lacquers and oils" what regards indoor environment (performance and indoor air).

Table 6.6

Evaluation Examples in Principles, Wood Floor

Product	Coating	Indoor Environment		Other aspects to be considered
		Function	Indoor Air
Floor	Wood with water-borne lacquer	/	/
	Wood with 2-comp. polyurethane lacquer			Special work environment legislation High VOC-content
	Wood with 2-comp. acid-curing lacquer		/	High VOC-content
	Wood with oil/alkyd			High VOC-content
	Wood pre- coated with UV-lacquer

	Among the best material
	Among acceptable materials
	Among the poorest materials/least acceptable materials

It should be stressed that the classification is only a general starting point, as it should always be complemented by considerations in relation to actual conditions.