O - is a gas. The methanol prevents polymerization to para-formaldehyde. If a formaldehyde container is found to have white needle crystals in the bottom, this is para-formaldehyde and poses no hazards beyond those of formaldehyde.
Some formaldehyde gas vaporizes from formalin and formaldehyde solutions.
Most of the vapor coming off, however, is trioxymethylene. The more dilute the solution, the less formaldehyde vapor which is released from the solution. Formaldehyde is intensely irritating to the mucous membranes and high concentrations are intolerable. Formaldehyde use is regulated by the OSHA Formaldehyde Standard 29 CFR 1910.1048 and by the Airborne Contaminants list 29 CFR 1910.1000 . The spill, if more than a de minimis quantity, must be handled by an organized spill team, using the incident command system.