The ventilation in nickel-cadmium battery shops is designed to provide how many air changes per hour?

• A. 1-2
• B. 3-4
• C. 5-6
• D. 7-8

Answer: (B)

The key idea is keeping the air in a nickel-cadmium battery shop moving enough to dilute hydrogen gas that is produced when the batteries are charged. Hydrogen is flammable, so you don’t want it to accumulate in the space. Ventilation is measured by how many times the room’s air is replaced each hour, and you need enough replacement to keep the gas well diluted but not so much that it wastes energy or creates disruptive drafts for workers and equipment. A moderate ventilation rate provides this balance: it dilutes any hydrogen to safer levels without the excess energy use or airflow issues that come with very high rates. The lower end risks insufficient dilution, while the higher end is more than what’s typically needed for normal operation, so the middle range is the practical, safety-conscious choice.