今泉設備株式会社, the prime contractor for the toilet renovation project at Nagaoka City Central Library, was instructed by Niigata Prefecture for failing to ensure workers received the required special education mandated by the Minister of Health, Labour and Welfare when assigning workers to Category 1 oxygen deficiency hazardous work between February 6 and 9, 2023. The company's legal representative was fined for violating the Labour Safety and Health Law, with the penalty confirmed on October 24, 2023. This violation falls under Article 28, Paragraph 1, Item 3 of the Construction Business Law. The prefecture mandated measures to prevent recurrence, including promptly informing employees of the violation and penalty, strengthening safety management systems at the workplace, complying with construction safety laws, and creating ongoing safety education plans for employees.