Construction Supervisor License Practice Exam

In the absence of manufacturer's instructions, how long may a straight run of a four-inch diameter dryer vent hose be?

1. 15'

2. 20'

3. 25'

4. 35'

The correct answer is: 35'

The standard length for a straight run of a four-inch diameter dryer vent hose, in the absence of manufacturer's instructions, is 35 feet. This guideline is established to ensure optimal airflow and efficiency for the dryer. Allowing for such a length helps maintain a proper balance in air movement and reduces the risk of lint build-up, which can lead to fire hazards. In practice, longer duct runs can lead to increased resistance to airflow, which diminishes the dryer’s performance. However, the code typically allows up to 35 feet to accommodate standard installation scenarios while still promoting safety and efficiency. After this length, every additional 90-degree bend or 45-degree bend in the duct would reduce the allowable length of the vent run to maintain effective performance.