Odor Problems in Toilets with Reduced Ventilation Frequencies Madoka Kimura, Takashi Akimoto, Nobuhiro Hirasuga, Yu Sakamoto, Sakurako Yamakita and Hikari Sakakibara E3S Web Conf., 111 (2019) 02025 Published online: 13 August 2019 DOI: 10.1051/e3sconf/201911102025