Conn. Agencies Regs. § 5-273-50
Any person, employer or subdivision thereof, or employee organization desiring to intervene in any proceeding shall file with the Board a sworn petition and four (4) copies thereof in writing, setting forth the facts upon which such person, employer or its subdivision thereof, or employee organization claims an interest in the proceedings. Such petition shall be served on all parties. Petitions shall be filed with the Board, with proof of service, at least two (2) days prior to the first hearing. Failure to serve or file such petition, as above provided, shall be deemed sufficient cause for the denial thereof, unless it shall be determined that good and sufficient reason exists why it was not served or filed as herein provided. The Board shall rule upon all such petitions and may permit intervention to such an extent and upon such terms or conditions as it shall determine may effectuate the policies of the Act.
Conn. Agencies Regs. § 5-273-50