AirTest PT9250 Manual Aplikasi - Halaman 4

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When a space is under-ventilated, CO

be very high (e.g. over 1500 ppm). Conversely,

concentration of CO

close to outside levels

(typically around 400 to 450 ppm) indicates very

high ventilation, or perhaps over-ventilation.

Levels of approximately 1100 ppm will indicate a

ventilation rate of 15 cfm per person, which is

typically required by most ventilation codes.

Spot Measurement Application Tips

Note CO

Is Not Harmful In Building

Environments: It is important to note that at the

levels we normally measure in buildings CO

itself is not harmful. In an occupational health

environment, exposure to CO

ppm over 8 hours, is considered acceptable by

OSHA.

In buildings the CO

more an indication of ventilation. If a space feels

uncomfortable, stuffy, or stale and the CO

are high, it is not really the CO

The high CO

levels are telling you that

ventilation is insufficient, and you are likely

reacting to all the things that build up when there

is insufficient fresh air ventilation.

Levels Must Be Stable For An Accurate

Spot

Ventilation

Measurement:

correlation between CO

rate can only be made by a spot measurement

when concentrations appear to have stabilized in

a space. If levels are continuing to change it may

be an inappropriate time to measure ventilation.

For low-density office spaces and retail

applications it is best to take measurements 2-3

hours after occupancy in the space has begun

(late morning or afternoon). In higher density

applications like school classrooms, theaters and

meeting rooms measurements can be made 15

to 20 minutes after the start of occupancy.

Avoid

Measurements

Economizer Is On:

Be aware that ventilation

rates will appear very high if the building is

operating in economizer mode (using outside air

for free cooling).

It is best to ensure the

economizer is temporarily disabled or not

operating

when

performing

measurements.

Measurement Location Tips:

will readily disperse and equalize within a space.

Therefore measurements can be taken just about

anywhere or at any height. However one should

keep away from open doors or windows as well

as the area directly surrounding a discharge grill.

Blowing Into The Sensor: Pure exhaled breath

contains 40,000 ppm of CO

disperse in air. Try to avoid breathing directly on

the sensor when taking a measurement. If you

do breath into the sensor, it will not hurt the

AirTest PT9250 & CO

Application Guide

levels will

levels up to 5,000

concentration is

levels

having the effect.

A true

levels and ventilation

When

Building

spot

Carbon dioxide

that will readily

sensor but it may take a few minutes for the

sensor to readjust to normal background levels.

Since the PT9250 measures up to 10,000 ppm

you may also temporarily send the display off

scale.

Estimating The Total Ventilation Rate To A

Space:

If you actually count the number of

people in the space when you take the

measurement, you can multiply this number

times the cfm-per-person ventilation rate to

determine the total amount of outside air being

delivered to the space.

Using Actual Outside CO

Ventilation Rate:

In some cases you may find

that the outside levels are slightly higher or lower

than the 400 ppm level assumed by the PT9250.

(A difference of about 50 ppm will result in an

error of about 0.5 cfm/person in the calculation.)

For a more accurate calculation of ventilation

rates you can reset the outside level used in the

PT9250 calculation based on actual conditions by

exposing the sensor to outside air. Once levels

have stabilized, press the power button for about

a second. The word "read" should flash on the

screen. Now the outside concentration you just

measured will be used for the calculation of

ventilation rate until you power off the sensor.

Once powered up again the sensor will assume

an outside level of 400 ppm until you power the

unit off.

Battery

Life: Battery life of the sensor is 8 to 14

hours. It is a good idea to charge the sensor up

every night. Regular charging will not hurt the

battery inside the PT9250.

Car Charging:

If desired you can also purchase

an automotive phone charger to keep the sensor

powered up between calls. Select a charger with

a 3.5 mm (od) connector that provides an output

voltage of 6 VDC with a current of 500 mA. The

plug-in is configured for positive in the center and

negative on the outer portion of the plug.

AirTest for further information.

Battery Charge Indicator:

charge level is indicated by the small graphic

symbol on the left side of the line dividing the

upper and lower display. Three bars indicate a

full charge.

Calibration:

There are a number of easy ways

to calibrate the sensor. These are discussed in

section 6 of this document.

Levels To Calculate

Call

The current battery

4 of