It's a level of formaldehyde, it relates to the composite wood product including laminate flooring, Carb 2 standard according to the California Environmental Protection Agency-Carb phase 2, E1 formaldehyde release is less than 0.5mg/lL E1 formaldehyde is less than 1.5mg/L. E2 formaldehyde release is less than 5 mg/L