How long should air be blown into a confined space before entering for ventilation?

Blowing air into a confined space for a minimum of 5 minutes before entering is crucial to ensure the safety of individuals. This duration allows for effective ventilation, helping to dilute and displace potentially hazardous gases or vapors that may be present in the space. Typical workplace safety guidelines suggest this timeframe as it likely provides enough time for fresh air to circulate and reduce the concentration of harmful substances, thereby minimizing the risk of asphyxiation or exposure to toxic agents. The chosen time frame supports the principle of ensuring adequate air quality prior to entry into potentially dangerous environments.