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Formaldehyde - test methods

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Emissions or content testing

  • A formaldehyde content test produces information on, how much formaldehyde is in the product.
  • A free formaldehyde content test tells about how much formaldehyde can be released during lifetime of the product.
  • An emissions chamber test shows the contribution of the product to indoor formaldehyde air concentration after a certain elapsed time.

Content testing

  • Some liquid products contain preservatives in bounded form from which formaldehyde is released slowly until the product is spread out on a surface.
  • Total formaldehyde tests set free all potentially formed formaldehyde at once.
  • Free formaldehyde determines actual formaldehyde concentrations in the product.
  • The details of the testing protocol (pH value, extraction agent etc.) determine to which extent formaldehyde is captured and analyzed, or hidden, with such testing methods.

Emissions testing

  • Case 1:

If formaldehyde is brought into the product and diffuses out slowly, then the normal VOC emissions test protocols can be applied to formaldehyde accordingly. Just the air sampling and analysis method has to be specific for formaldehyde (e.g. the acetyl acetone method, as in EN 717-1) or for volatile aldehydes in general (the DNPH method, as in TS / EN 16516, ISO 16000-3, CDPH method, ASTM D5197 and more).

An emissions chamber test shows the contribution of the product to formaldehyde air concentration after a certain elapsed time - in Europe after 3 and/or after 28 days, and in the USA after 14 days, or after 7 days for furniture, or after 20 hours for wood-based panels in a large test chamber. All these approaches serve as indicator for long-term indoor air exposure.

  • Case 2:

If formaldehyde is produced continuously, e.g. by hydrolysis of a binder in contact with normal air humidity, then a steady-state-concentration will be reached in a test chamber, typically after some days or weeks. Several test methods determine the steady-state-concentration by taking air samples almost every day to establish the decay curve. Then it is calculated which concentration will be the stable one, and when this will be reached, from that decay curve (EN 717-1, ISO 12460-1, ASTM D6007).

In most cases, the steady-state-concentration and the emissions test result after 28 days correlate well, as long as the testing parameters are similar.

Parameters influencing the emissions test

  • Temperature:
    • For most products, higher temperature will increase the formaldehyde concentration early during the test. Later during the test it cannot be predicted whether higher temperature increases or decreases the test result. 
    • Higher temperature will increase the steady-state-concentration in the case of continuous formation of formaldehyde in the product.
    • The impact of temperature cannot be predicted or calculated, except for products containing urea-formaldehyde binders where such calculation models exist (the "Anderson formula", as in ASTM D6007 and ASTM E1333).
  • Air humidity:
    • For most products, within the standard range of 45 - 55 % RH, there is no large impact on the test result. This was shown during validation of CEN/TS 16516, see below.
    • Higher relative humidity will increase the steady-state-concentration in the case of continuous formation of formaldehyde in the product.
    • The impact of air humidity cannot be predicted or calculated, except for products containing urea-formaldehyde binders where such calculation models exist (the "Anderson formula", as in ASTM D6007 and ASTM E1333).
  • Ventilation:
    • Higher ventilation dilutes any emissions that are determined in a test chamber with more clean air.
      • In terms of air concentration, the result will be lower with higher ventilation, due to dilution.
      • But in terms of emissions rate per area and hour, the result should be the same for most products.
      • Validation of CEN/TS 16516 showed that a recalculation of air concentrations between different ventilation rates is possible in a range of 0.25 - 1.5 air changes per hour.
    • In the case of continuous formation of formaldehyde in the product, higher ventilation can expose the test specimen to more water from air humidity than with lower ventilation. In that case, the above stipulated constancy of the emissions rate of formaldehyde might be challenged.
  • Loading factor
    • The loading factor determines the size of the test specimens to be tested, relative to the volume of the test chamber or of the reference room. The loading factor is expressed as m²/m³ in most cases.
    • Higher loading factor includes larger source of the emissions and thus gives higher emissions.
      • In terms of air concentration, the result will be higher with higher loading factor, due to larger emissions source.
      • But in terms of emissions rate per area and hour, the result should be the same for most products.
      • Validation of CEN/TS 16516 showed that a recalculation of air concentrations between different ventilation rates is possible in a range of 0.004 - 2.0 m²/m³.

Correlation between TS / EN 16516 and EN 717-1 / E1 class

EN 717-1 (which is the basis of E1 formaldehyde class), in comparison with TS / EN 16516 and ISO 16000, operates with

  • the same testing temperature;
  • 1.0 air change per hour (EN 717-1) instead of 0.5;
  • a fixed loading factor of 1.0 (EN 717-1), instead of loading factors depending on the application scenario, such as floor, wall etc.;
  • and EN 717-1 prefers air sampling and monitoring with the acetyl acetone method, but it allows the use of the DNPH method (ISO 16000-3 and TS / EN 16516) as well, as these are known to be equivalent for formaldehyde.

As outlined above, these differences should be not significant for most products. It could be shown during the validation of CEN/TS 16516 that EN 717-1 and the CEN/TS 16516 give the same results after 28 days in test chambers within the measurement uncertainty, when the emission rates are compared. Different ventilation rates during testing then are leveled out by calculation of the final test result from the emission rate. See www.centc351.org/ and the validation report, clause 5.2 on page 48.

In that study, this held true also for the tested wood-based panel. But it can be imagined, that some panels might show differences in the emission rate and thus would need more detailed investigation.

Can TS / EN 16516 and ISO 16000 tests be used to determined E1 class compliance of a product?

Yes and no.

It cannot be used if you read the letters of the standards alone, because TS / EN 16516 and ISO 16000 do not determine the steady-state concentration.

But TS / EN 16516 and ISO 16000 test results obtained after 28 days can be used if the following considerations can be accepted:

  • The steady-state concentration is assumed to be stable after some days or weeks. Then the 28 days emissions are the same as the steady-state concentration.
  • The differences in ventilation rate and loading factor can be re-calculated via the emission rate, as described in TS / EN 16516. And if a product complies after being tested at a lower ventilation than specified in EN 717-1 even without re-calculation, then it complies in any case.
  • The higher relative air humidity in TS / EN 16516 and ISO 16000 (50% RH) will lead to higher test results; if the product still complies with E1 class limits, then it will certainly do so when tested at 45% RH as in EN 717-1.

Can US and ASTM tests be used to determined E1 class compliance of a product?

Also here, it is possible if the following considerations can be accepted:

  • The ventilation rate during testing is close to EN 717-1 ventilation rate for all these standards.
  • Some US standards (ASTM E1333, ASTM D6007) operate at a higher test temperature than the other standards which gives higher test results (25 °C versus 23 °C in Europe).
    • If a product nevertheless fulfills the requirements, then it would also comply with EN 717-1 tests (which is the basis of E1 formaldehyde class).
  • Several of the US standards (ASTM D5116, ASTM D6670, CDPH, ANSI/BIFMA M7.1) have a shorter testing duration than EN 717-1 (which goes for testing until equilibrium, but not longer than 28 days). This may lead to higher test results if equilibrium is not reached when the US test was stopped.
    • If a product nevertheless fulfills the requirements, then it would also comply with EN 717-1 test.

Correlation of emissions tests with simpler secondary test methods

A number of simpler tests are in use for daily factory production control, and sometimes even for evaluation of formaldehyde product emissions:

  • Gas analysis: EN 717-2, ISO 12460-3;
  • Flask test: EN 717-3;
  • Perforator test: EN 120, ISO 12460-5;
  • Desiccator test: ISO 12460-4, ASTM D5582, JIS A1460.

All these tests can be applied if a correlation between the emissions chamber test and the secondary test method is applied. But these correlations are not universal. They have been established for some types of wood-based panels. But the correlation is different as soon as the top layer changes, a different binder is used, or the density of the material deviates.

Therefore equivalency between EN 717-1 and the other tests (such as EN 120) is valid only for a certain, well investigated product type, and you will see the name of the product type in any comparison tables that deliver correlation factors, as e.g. in EN 13986 for different groups of wood-based panels.

Using synergies

If a manufacturer needs formaldehyde and VOC emission testing for markets in several countries, then Eurofins can try to help saving money by combining all required testing into one test setup, and by selecting the worst-case test method to obtain test data covering all requirements. This service is unique in the whole world. No single other testing laboratory is approved for emission chamber testing by the same number of both US and European specifications and regulations for low-emitting products.

If it comes to formaldehyde, this combination of different test methods into one test setup requires a certain pragmatic creativity. The different test methods deliver more or less different test results for the same product sample. But in two cases this does not matter for product evaluation:

  • If a product complies with a test method that gives systematically higher values than the reference test method, then it will comply with that test method as well; and
  • If a product gives test results far below the limit values, much lower than the discrepancy between the test methods, then it will comply with the reference test method as well;
  • Nevertheless, these considerations might be rejected by regulators and programs that are run by non-experts; administrative staff may want to stick to the printed letter and not accept such analogy conclusions. This has to be clarified in each single case.

Contact VOC Testing Laboratories

Please see here contact information of Eurofins VOC testing laboratories in Europe, China and Japan:
www.eurofins.com/voc-contacts.