Space Length =20 feet
Space Width = 10 feet
Space Height =10 feet
Volume (L x W x H) = 2000 cubic feet
The fan to be used is the VAF-200 that has a free air flow of 800 CFM which would change the air in the confined space in 2.5 minutes or 24 times an hour
(2000 cubic feet divided by 800).
In this example the VAF-200 would be suitable.

## How to Calculate a confined space

VAF Air recommends that you change the air in a confined space at least 20 times
each hour, or once every 3 minutes. Where possible we would always recommend
that you not only extract the air but also utilize a blower to push clean air into the
workspace. The Miniveyor Air VAF fans work on both positive and negative air flow,
so are equally at home extracting as well as blowing. To use this recommended
method, you would need 2 or more openings to your confined workspace and
employ 2 fans. If you only have 1 opening, then you should use positive airflow
and use the fan to blow air into the confined workspace.
To determine which of our exhaust blowers is suitable for your application you
must first calculate the volume of your confined workspace.
If the space is a regular shape (cube or rectangle) then you would simply multiply
the length by the width, and then finally by the height. It is important that you use
the same unit of measurement as used to rate the fan. You should use either feet
or meters as our blowers are rated in either cubic feet per minute (CFM) or cubic
meters per hour (m³/hour).
If the workspace is not rectangular or cube, simply divide the space into smaller
rectangular spaces to help you calculate the volume.
For cylindrical spaces, such as tanks, pipes or silos calculate the volume using Pi
(3.142) x the radius squared x the length.

# CFM Example (Imperial units)

Space Length =20 feet
Space Width = 10 feet
Space Height =10 feet
Volume (L x W x H) = 2000 cubic feet
The fan to be used is the VAF-200 that has a free air flow of 800 CFM which would change
the air in the confined space in 2.5 minutes or 24 times an hour (2000 cubic feet divided
by 800).
In this example the VAF-200 would be suitable.
Space Length =6 meters
Space Width = 4.5 meters
Space Height = 4.5 meters
Volume (L x W x H) = 121 cubic meters
Again we want to use the VAF-200 which has a rating of 1350 cubic meters per hour
(m³/hour).
Multiply the volume by 20 (minimum number of air changes required) to give the
required fan rating.
121m³ x 20 = 2420 m³/hour
In this example the VAF-200 would not be suitable when used as a single fan as the
required air flow is below that of the VAF-200.
You would have 2 solutions-
Solution 1: Stack 2 VAF-200 fan units to multiply the air flow to 2700 m³/hour
Solution 2: Alternatively use the VAF-300 which has a free air flow 3400 m³/hour

# m³/hour Example (Metric units)

# Blower Selection

# *WARNING

### Always assume a confined

### space work area is con-

### taminated until it has been

### proven safe for work per-

### sonnel. You should

### NEVER enter a confined

### space work area until it

### has been thoroughly

### tested with appropriate

### gas detection equipment

### and proven safe for work

### personnel.