Final answer:
The maximum diameter of a sphere that should not pass through guards on stairways or balconies is typically 4 inches (10 cm) to ensure safety, according to current building codes and standards.
Step-by-step explanation:
When discussing the maximum diameter of a sphere that should not pass through the required guard on a stairway, porch, balconies, and landings, the subject revolves around building codes and safety standards typically set forth in engineering and architectural guidelines. The specific measurement can vary based on local regulations, but the intent is to prevent accidents, such as small children getting their heads stuck between the rails or falling through openings.
For instance, an older "rule of thumb" was that a sphere with a diameter equivalent to the opening should not exceed 4 inches (approximately 10 cm). More recent safety standards recommend that this opening not allow a sphere greater than 4 inches to pass through, aiming to create a safer environment on structures like balconies and stairways.