Board Formaldehyde Inspection

Panel formaldehyde testing mainly conducts scientific testing and analysis on formaldehyde emission, free formaldehyde content, formaldehyde content by perforation extraction method, surface formaldehyde concentration, formaldehyde emission rate decay curve and formaldehyde emission characteristic parameters, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Formaldehyde emission: This is the core item of panel formaldehyde testing, referring to the mass or concentration of formaldehyde released into the air by a unit area of the panel under specified test conditions. It is usually expressed in mg/m³ or mg/(m²·h), directly reflecting the indoor air pollution level that the panel may cause in the service environment, and is the most critical indicator for evaluating its environmental performance.

Free formaldehyde content: Refers to the ratio of the mass of formaldehyde that does not participate in chemical reactions and exists in a free state inside the panel to the total mass of the panel, usually expressed in mg/100g. This indicator reflects the total amount of formaldehyde contained in the panel itself that may be gradually released in the future, and is an important basis for evaluating its potential release risk, especially crucial for raw material quality control of wood-based panels.

Formaldehyde content by perforation extraction method: The total extractable formaldehyde content in the panel is determined by the perforation method, in mg/100g. This method simulates the extreme conditions of high temperature and high humidity, extracting all formaldehyde that may be released from the panel (including free and partially bound forms), and is used to evaluate the total formaldehyde content of the panel. It is a commonly used mandatory test item in Europe and other regions.

Surface formaldehyde concentration: In a specific sealed environment, a portable detector or sampling method is used to directly measure the instantaneous formaldehyde concentration in the air near the panel surface. This item is commonly used for rapid screening at construction sites or on-site evaluation of installed panels, but the results are easily disturbed by factors such as ambient temperature, humidity and air flow velocity, and need to be interpreted with caution.

Formaldehyde emission rate decay curve: Through long-term tracking tests, the pattern of the formaldehyde emission of the panel changing with time is studied and the emission rate decay curve is plotted. This analysis helps to predict the formaldehyde release trend of the panel at different use stages, evaluate its long-term environmental safety, and provide data support for the dynamic evaluation of indoor air quality.

Formaldehyde emission characteristic parameters: Including the diffusion coefficient and the initial emittable concentration, etc., which are used to deeply characterize the formaldehyde release process of the panel through mathematical models (such as mass transfer models). These parameters can more fundamentally reflect the migration and release mechanism of formaldehyde inside the panel, and are used to predict the release behavior under different environmental conditions. They belong to higher-order scientific research analysis items.

Testing Scope

Plywood: A board material of three or more layers made by rotary cutting logs into veneers or planing wood into thin wood, and then bonding them with adhesive. Its formaldehyde release mainly comes from adhesives such as urea-formaldehyde resin and phenolic resin used in lamination. During testing, the sampling position and test method need to be distinguished according to the thickness, number of layers and adhesive type.

Particleboard: Also known as chipboard, it is a wood-based panel made by cutting wood or other lignocellulosic materials into fragments of a certain specification, drying, applying adhesive and hot pressing. Due to the large use of formaldehyde-containing adhesives and the large specific surface area, the formaldehyde release problem is relatively prominent, making it a key testing object. The influence of its density and adhesive application amount on the results needs to be paid attention to.

Fiberboard: Including medium density fiberboard and high density fiberboard, made from wood fibers or other plant fibers as raw materials, with synthetic resin applied and pressed by heating. Its internal structure is uniform, and the formaldehyde release is relatively slow but persistent. During testing, attention should be paid to the sealing effect of its thickness and later surfacing treatment (such as veneering and painting) on the release.

Blockboard: Commonly known as the core board, it is made by gluing and pressing a spliced wood board between two veneers. Its formaldehyde release sources mainly come from the adhesive used for the spliced wood strips in the middle and the glue layers of the upper and lower surface boards. During testing and sampling, both the core strips and the surface boards need to be taken into account, and the overall release level is significantly affected by the core strip material and splicing process.

Surfaced wood-based panel: Refers to panels with decorative materials (such as impregnated paper film, veneer and PVC) applied on the surface of wood-based panel substrates such as particleboard and fiberboard. During testing, it needs to be clarified whether the overall emission of the "surfaced panel" is tested, or whether the shielding effect of the surfacing on the formaldehyde emission of the substrate is evaluated. The test conditions need to simulate the actual use state.

Glued laminated timber and finger-jointed board: Made by longitudinally splicing short square timbers with adhesive. Although the amount of adhesive used is relatively small, there are many glue joints and the formaldehyde release channels are complex. The testing scope needs to cover different wood species, finger-joint processes and the types of splicing adhesives used, evaluating their comprehensive release characteristics.

Testing Methods

1 m³ chamber method: An internationally recognized method. The sample is placed in a standard climate chamber with strictly controlled temperature, humidity and air exchange rate. After stabilization, the air in the chamber is collected and the formaldehyde concentration is determined by the acetylacetone spectrophotometric method or high-performance liquid chromatography. This method is closest to the actual service environment of the panel, gives accurate and reliable data, and is the core arbitration method of standards such as GB 18580-2025.

Desiccator method: The sample is placed at the bottom of a desiccator, with an absorption dish placed above. In the sealed desiccator, the formaldehyde released by the sample is absorbed by distilled water, and after a certain time, the formaldehyde content in the absorption solution is determined. This method has simple equipment and convenient operation, is widely used in Japanese JIS standards and early Chinese standards, and is suitable for rapid comparative tests.

Perforation extraction method: After crushing the sample, toluene solvent is used to heat and reflux in a perforation extractor to extract all the formaldehyde from the panel, which is then converted into an aqueous solution for determination. This method measures the "total formaldehyde content" rather than the emission, with stable results and good reproducibility. It is the main method for determining content in European EN standards and Chinese standards.

Gas analysis method: The sample is placed in a test chamber with constant temperature, humidity and air flow velocity. After the air flows over the sample surface, the formaldehyde concentration in the outflow gas is continuously and online determined by a detector (such as a photoionization detector). This method can monitor the release dynamics in real time and obtain release rate data, and is mostly used in research fields and some ASTM standards.

Acetylacetone spectrophotometric method: Formaldehyde reacts with acetylacetone in the presence of ammonium salts to generate a stable yellow compound, diacetyldihydrolutidine, which is determined by colorimetry at a wavelength of 412 nm. This method is a classic chemical analysis method for determining the formaldehyde concentration in aqueous solutions, with high sensitivity and good selectivity, and is the nationally specified method for the downstream analysis of the chamber method and the desiccator method.

High-performance liquid chromatography: Formaldehyde is derivatized with 2,4-dinitrophenylhydrazine to generate a stable hydrazone compound, which is separated by high-performance liquid chromatography and analyzed qualitatively and quantitatively with a UV detector. This method has strong anti-interference ability, high accuracy and precision, and is especially suitable for the precise determination of complex matrices or low-concentration samples. It is an important arbitration and verification method.

Testing Standards

Domestic Standards:

1. GB 18580-2025, Indoor decorating and refurbishing materials — Limit of formaldehyde emission of wood-based panels and finishing products

2. GB/T 17657-2022, Test methods of evaluating the properties of wood-based panels and surface decorated wood-based panels

3. GB/T 1931-2009, Method for determination of moisture content of wood

4. GB/T 1936.1-2009, Method of testing in bending strength of wood

5. GB/T 4823-2013, Defects in sawn timber

International Standards:

1. ISO 12460-1, Determination of formaldehyde emission of wood-based panels — Part 1: 1 m³ chamber method

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Climate chamber: With a volume usually of 1 m³, inert inner walls, and equipped with a high-precision temperature and humidity control system (such as 23±0.5 ℃ and 45±3% RH), an air purification system, a constant-flow air exchange device (usually 1.0±0.05 times/h) and an air mixing fan. It is the core equipment for simulating the real indoor environment and obtaining formaldehyde emission data, with extremely high requirements for construction and operation maintenance.

Perforation extractor: A glass instrument system composed of a round-bottom flask, a perforator, a condenser and a liquid seal device. It is used to extract formaldehyde from the panel by heating and refluxing in toluene solvent. The ground glass joints are required to be tightly connected and the heating power stable and controllable, ensuring that the extraction process is complete and leak-free. It is a dedicated device for obtaining formaldehyde content data.

Spectrophotometer: Used for the determination of formaldehyde concentration by the acetylacetone spectrophotometric method. It requires high wavelength accuracy, transmittance correctness and stability, and is equipped with cuvettes of 1 cm or longer. Before testing, a standard curve needs to be drawn with formaldehyde standard solutions, and the instrument regularly calibrated to ensure the accuracy of absorbance readings.

High-performance liquid chromatograph: Mainly composed of a solvent delivery pump, a sample injector, a chromatographic column, a UV detector and a data processing system. It is used for trace analysis of formaldehyde, requiring low baseline noise, good retention time repeatability and high separation efficiency of the chromatographic column for the target derivatives. Standard substances need to be used for regular calibration, and the derivatization reaction conditions strictly controlled.

Constant temperature and humidity chamber: Used for the conditioning of samples before testing and the environmental control during processes such as the desiccator method. The temperature and humidity in the chamber are required to be uniform and stable (such as temperature 23±1 ℃ and humidity 50±5%), with small fluctuation, to ensure that all samples are in a unified equilibrium state before testing and reduce the error caused by pretreatment.

Air sampler: Including constant-flow air samplers, bubbling absorption tubes (or impinging absorption bottles), etc. It is used to collect formaldehyde in the climate chamber air or on-site air, requiring accurate and stable flow (such as 1.0 L/min) and the ability to work continuously for a long time. The absorption solution (usually distilled water) in the absorption tube needs to ensure absorption efficiency.