How the QuantiFit2 Works
4
The QuantiFit2 functions by creating and maintaining a negative pressure in the respirator. Once
the adapter valve is closed, sealing the respirator, the QuantiFit2 removes air from the respirator
until the challenge pressure is reached.
When the challenge pressure is reached, if there isn’t a leak, the QuantiFit2 doesn’t remove any
more air from the respirator. If there is a leak, air enters the respirator. The QuantiFit2 then
removes air from the respirator until the challenge pressure returns to the targeted value. This
process continues for 8 seconds, and then the test step ends.
During the fit test, the QuantiFit2 measures exactly how much air the instrument removed from
the respirator after reaching the challenge pressure. This measurement is equivalent to the leak
rate.
Challenge pressure, expressed in inches of water, is the maximum partial vacuum created in a
correctly fitting respirator when the user is working at a moderate to high rate. The modeled
breathing rate is the calculated total inspiration for one minute.
The modeled breathing rate is expressed in liters per minute (LPM), and is multiplied by 1,000 to
provide cc/min, it is then divided by the leak rate in cc/min. This is the fit factor ratio. It is a ratio
of the total inhalation pressure to the air that leaked into the respirator.
Fit Factor Explanation
The ratio of the modeled breathing rate to the measured leak rate is the calculated fit factor and
is expressed by the following equation:
The modeled breathing rate (MBR) is the rate at which an individual could be expected to
breathe under moderate to heavy working conditions. The MBR is predetermined for the
standard respirator types. The MBR is calculated from the parameters specified by the operator
for custom respirators.
The measured leak rate (MLR) is directly related to respirator fit and integrity. All fit factors are
calculated from the MLR. The QuantiFit2 directly measures air leakage in cubic centimeters per
minute (cc/min) and then calculates the fit factor (FF).
The overall fit factor is calculated by using the harmonic mean of the fit testing steps as follows:
Where:
N = The number of exercises;
FF1 = The fit factor for the first exercise;
FF2 = The fit factor for the second exercise;
and FFN = The fit factor for the nth exercise
Summary of Contents for QuantiFit 2
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