The temperature danger zone describes temperatures that allow many foodborne bacteria to grow readily. US consumer guidance commonly uses 40–140°F (about 4–60°C). Time in this range matters as well as temperature.
Use rapid cooling for cooked perishables, keep hot food hot, and use a thermometer. Do not use smell or appearance as a safety test. Food-service rules may use different boundaries and detailed time controls; follow the guidance appropriate to the setting rather than mixing standards.
Reference: Further reading.