According to International Composite Board Emission Standards (ICBES), there are 3 European formaldehyde classes, namely: E0, E1 and E2. This classification is based on the measurement of formaldehyde emission levels. For instance, E0 is classified as having less than 3 milligrams of formaldehyde out of every 100 grams of the glue used in particleboard and plywood fabrication. E1 and E2, conversely, are classified as having 9 and 30 grams of formaldehyde per 100 grams of glue respectively.