Because most office buildings are cleaned while they are empty, many cleaning workers work evening hours. Some, however, such as school and hospital custodians, work in the daytime. When there is a need for 24-hour maintenance, janitors may be assigned to shifts. Most full-time building cleaners work about 40 hours a week. Part-time cleaners usually work in the evenings and on weekends.

Building cleaning workers usually work inside heated, well-lighted buildings. However, they sometimes work outdoors, sweeping walkways, mowing lawns, or shoveling snow. Working with machines can be noisy, and some tasks, such as cleaning bathrooms and trashrooms, can be dirty and unpleasant. Janitors may suffer cuts, bruises, and burns from machines, handtools, and chemicals.