For formaldehyde solutions containing more than 10% formaldehyde, see separate entry in this table for "Biological specimens in preservative solutions."
Quantity limits: None*
Formaldehyde solutions of less than 10% are not restricted as hazardous materials. Leakproof packaging with absorbent material is still strongly encouraged.
Tip: Full-strength "Formalin" is typically 35%-40% formaldehyde by volume. So a solution that is less than 25% Formalin would be less than 10% formaldehyde and not restricted.
*Liquids, gels, and aerosols in carry-on baggage are further limited to 100-ml (3.4 oz) containers at the TSA security checkpoint.