Hygienic means that something is clean, sanitary, and in conformity with health care requirements.
Indoor environment refers to a space that is inside a building, and in which people spend time. An indoor environment may be e.g. a single room, the lobby of a public building, a waiting area or operating room of a hospital, or the bathroom of a residence.
An indoor environment includes indoor air, surfaces and water (if there is a water outlet in the space).
Hygienic indoor environment refers to an indoor space in which particular attention has been given to sanitariness and cleanliness, by using solutions and products that, in and of themselves, increase the cleanliness and sanitariness of the space.