If there are 2 entry/exit points into the confined space, what ventilation arrangement may be provided at one entry/exit and to the other?

If there are 2 entry/exit points into the confined space, what ventilation arrangement may be provided at one entry/exit and to the other?

• A. NPV to one and PPV to the other
• B. PPV to both
• C. NPV to both
• D. No ventilation required

Answer: (A)

With two entry/exit points, you want air to move through the space from one side to the other. This is cross-ventilation: use a positive pressure ventilation (supply) at one opening to push fresh air in, and a negative pressure ventilation (exhaust) at the opposite opening to pull air and contaminants out. The flow from the clean-air supply toward the exhaust creates a controlled path that dilutes and removes hazardous gases and smoke, keeping the atmosphere safer for anyone inside or assisting from outside. Using supply fans at both openings would push air in from both ends but might not effectively remove contaminants, potentially driving smoke or gas toward the other entrance. Exhausting from both ends could pull air out without delivering enough fresh air inside. No ventilation would leave the space stagnant and hazardous.

With two entry/exit points, you want air to move through the space from one side to the other. This is cross-ventilation: use a positive pressure ventilation (supply) at one opening to push fresh air in, and a negative pressure ventilation (exhaust) at the opposite opening to pull air and contaminants out. The flow from the clean-air supply toward the exhaust creates a controlled path that dilutes and removes hazardous gases and smoke, keeping the atmosphere safer for anyone inside or assisting from outside.

Using supply fans at both openings would push air in from both ends but might not effectively remove contaminants, potentially driving smoke or gas toward the other entrance. Exhausting from both ends could pull air out without delivering enough fresh air inside. No ventilation would leave the space stagnant and hazardous.