CIH - Certified Industrial Hygienist Engineering Controls and Ventilation Questions and Answers

Question 1

An industrial hygienist is designing a local exhaust ventilation (LEV) system for a process that releases contaminant with low velocity into moderately still air. According to ACGIH's 'Industrial Ventilation: A Manual of Recommended Practice,' which of the following capture velocity ranges would be most appropriate for the hood design?

Accepted Answer

50 - 100 fpm

Answer

According to the ACGIH Industrial Ventilation Manual, a capture velocity of 50-100 fpm is recommended for contaminants released with low velocity into moderately still air, such as evaporation from tanks or degreasing operations. Higher velocities are needed for more energetic release conditions.

Question 2

A paint spray booth has an opening that is 7 feet high and 10 feet wide. To maintain worker protection, the design specification requires an average face velocity of 125 feet per minute (fpm). What is the required airflow rate (Q) in cubic feet per minute (CFM)?

Accepted Answer

8,750 CFM

Answer

The required airflow rate (Q) is calculated using the formula Q = V × A, where V is the face velocity and A is the cross-sectional area of the opening. The area (A) is 7 ft × 10 ft = 70 sq ft. Therefore, Q = 125 fpm × 70 sq ft = 8,750 CFM.

Question 3

Which of the following describes the primary function of a flange on an unflanged local exhaust hood?

Accepted Answer

To create a barrier that prevents air from being drawn from behind the hood, improving capture efficiency.

Answer

A flange on a local exhaust hood serves as a plane of symmetry, effectively blocking airflow from the zone behind the hood. This forces more air to be drawn from the contaminant source in front of the hood, thereby increasing its capture efficiency for the same amount of airflow.

Question 4

According to the hierarchy of controls, which of the following is considered the most effective method for controlling workplace hazards?

Accepted Answer

Elimination or Substitution

Answer

The hierarchy of controls, as recognized by NIOSH and OSHA, ranks hazard control methods by effectiveness. Elimination (physically removing the hazard) and Substitution (replacing the hazard with a less hazardous alternative) are at the top of the hierarchy and are considered the most effective control strategies.

Question 5

A pitot tube traverse in a circular duct measures an average velocity pressure (VP) of 0.64 inches of water gauge (w.g.). Assuming standard air density, what is the approximate air velocity (V) in the duct?

Accepted Answer

3204 fpm

Answer

The relationship between velocity pressure and velocity for standard air is given by the formula V = 4005 * sqrt(VP). In this case, V = 4005 * sqrt(0.64). The square root of 0.64 is 0.8. Therefore, V = 4005 * 0.8 = 3204 fpm.

CIH - Certified Industrial Hygienist Exam Practice Test

CIH - Certified Industrial Hygienist Exam Practice Test

CIH - Certified Industrial Hygienist Engineering Controls and Ventilation Questions and Answers