Exposed rectangular ducts of 14 inches or less, when serving a single dwelling unit, shall be constructed of _______ gauge steel.

Exposed rectangular ducts of 14 inches or less, when serving a single dwelling unit, shall be constructed of _______ gauge steel.

• A. 30
• B. 24
• C. 28
• D. 26

Answer: (C)

Exposed rectangular ducts in residential work are given a minimum metal thickness to ensure they stay rigid and resist denting when they’re visible and subject to handling. For small ducts—14 inches or less—in a single dwelling unit, the standard specifies 28 gauge steel. This thickness strikes a practical balance: it’s strong enough to maintain shape and resist minor damage during installation and service, yet light enough to keep installation simple and cost-effective. If the duct were larger or not exposed, or if it served a different occupancy, a thicker gauge (such as 26 or 24) might be required to provide the necessary strength. Remember, gauge relates to thickness (lower numbers are thicker, higher numbers are thinner), so 28 gauge is a relatively light but acceptable thickness for these small, exposed residential ducts.

Exposed rectangular ducts in residential work are given a minimum metal thickness to ensure they stay rigid and resist denting when they’re visible and subject to handling. For small ducts—14 inches or less—in a single dwelling unit, the standard specifies 28 gauge steel. This thickness strikes a practical balance: it’s strong enough to maintain shape and resist minor damage during installation and service, yet light enough to keep installation simple and cost-effective. If the duct were larger or not exposed, or if it served a different occupancy, a thicker gauge (such as 26 or 24) might be required to provide the necessary strength. Remember, gauge relates to thickness (lower numbers are thicker, higher numbers are thinner), so 28 gauge is a relatively light but acceptable thickness for these small, exposed residential ducts.