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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties


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Link to relevant study record(s)

Description of key information

extremely flammable (gas)
flammable liquid (aqueous solution >10% methanol)
combustible liquid (aqueous solution ≤10% methanol)

Key value for chemical safety assessment

Additional information

Flammability of pure formaldehyde:

The flammability of pure formaldehyde gas is derived from the explosive limits. Eight sources were identified concerning the explosion limits of formaldehyde in air. Six authoritative (online) handbooks all reporting lower explosion limits of 7 and higher explosion limits of 72 or 73 %. CRC (2010), GESTIS (2015), Knovel database (2012), RömppChemie (2015), Chemsafe (2015) as well as by Ullmanns dictionary (2012). According to a report from the INCHEM (1991) the explosion limits are between 12.5 and 80%. In a study performed by BASF (1988) the upper and lower explosion limits of a aqueous solution containing 55% formaldehyde were determined to be 37.4 % and 61.8 % for the lower and upper explosion limit at 78 °C and 89°C respectively. However, the method applied for this test is slightly unconventional since these limits usually apply to a concentration at 20 or 25 °C. Based on the results gathered from the online databases and available handbooks the lower and upper explosion limits for formaldehyde are determined to be 7% and 73% respectively.

Flammability of aqueous formaldehyde solution

Flammability is derived from flash point and boiling point.

Based on chemical structure pyrophoric properties and flammability in contact with water are not to be expected.

The substance or mixture does not need to be classified as self-heating as the substance is a liquid.

Justification for classification or non-classification

Formaldehyde Gas:

Since the substance is igniteable when in a mixture of 7 - 73 % by volume in air, it has to be classified as Flammable gas category 1: H220 extremely flammable gas in accordance with Regulation (EC) No. 1272/2008 and GHS.

Aqeuous solution (≤10% methanol):

Since the flash point of the substance will be in the range of 60 to 93 °C, the substance does not need to be classified for flammable liquids in accordance with Regulation (EC) No. 1272/2008, but according to GHS should be classified as category 4 (combustible liquid).

Aqueous solutions (>10% methanol):

As the flash point of the substance will be in the range of 23 to 60 °C, the substance has to be classified as Category 3: H226: Flammable liquid and vapour in accordance with Regulation (EC) No. 1272/2008 and in accordance with GHS.