# How do you find average face velocity?

## How do you find average face velocity?

Average face velocity is calculated by dividing the sash opening into one-foot squares. Velocity readings are taken in each grid area and averaged.

## Why is face velocity important?

Face Velocity is a measurement of the speed at which air enters a fume hood’s face opening. And if face velocities are set too low, the hood will not be adequately exhausting dangerous fumes, vapors, gasses, dust, or the like, from the room.

What is face velocity of fume hood?

The face velocity is related to the amount of air being pulled through the fume hood, or the volumetric rate. This number is typically measured in cubic feet per minute (CFM). The more air that is pulled through a fume hood’s openings, the faster the air will travel.

### What is the minimum value of face velocity permitted for the smoke champ?

Standard Z9. 5-1992 Section 5.7 requires that, “Each hood shall maintain an average face velocity of 80-120 fpm with no face velocity measurement more than plus or minus 20% of the average.”

### How do you calculate the face velocity of a fume hood?

1. Fume HoodAirflow – Cubic Feet per Minute (CFM) Calculation Explained.
2. FACE OPENING Calculation: 22” x 12” = 264 square inches. Divide this by 144 to get Square Feet. 264 ÷ 144 = 1.83 square foot opening.
3. 1.8 square feet x 100 fpm = 180 CFM.

How do you check fume hood face velocity?

Divide the fume hood opening into equal grids with sides measuring no more than 12-inches (approximately 6 grids). The tip of the Vane anemometer probe shall be positioned in the plane of the sash opening. Each grid velocity shall be the average of at least 10 measurements made over at least 10 seconds.

#### What is face velocity?

Face velocity is the measured air speed at an inlet or outlet of a heating ventilation and air conditioning (HVAC) system. For example, a fume hood is a ventilated enclosure that is used to safely handle harmful or toxic fumes or vapours.

#### What face velocity is required to achieve?

ANSWER: 8.5 m/s [850 cm/s).

How is fume hood face velocity calculated?

Airflow into a hood is achieved by an exhaust blower which ‘pulls’ air into and through the hood and exhaust system. The resulting ‘pull’ at the opening of the hood is measured as face velocity. Face velocity is measured in m/s and can be calculated as the volume flow rate (m³/s) divided by the face area (m²).

## What is the minimum distance from the front of the fume hood should you work?

The user’s unobstructed personal work area should extend at least 4′ 6” from the face of the fume hood. 5. The distance between the sash and an opposing wall or other obstruction likely to affect the air flow should be at least 6′ feet.

## What is the OSHA regulatory statement concerning face velocity of air flow for safety fume hoods?

OSHA: “General air flow should not be turbulent and should be relatively uniform throughout the laboratory, with no high velocity or static areas; air flow into and within the hood should not be excessively turbulent; hood face velocity should be adequate. (Typically 60-110 fpm.)”

What instrument would you use to measure the face velocity of a fume hood?

Fume Hood Flow Meter Information and Instructions The pressure gauges are mechanically simple and measure and display negative pressure inside the exhaust duct (above the hood) relative to the room pressure. The digital monitors need electrical power to measure the velocity of the airflow into the hood.