• Measures carbon dioxide levels, air temperature and humidity
• Calculates dew point and wet bulb temperature
• Maintenance free NDIR (non-dispersive infrared) CO2 sensor
• Carbon Dioxide reading displayed in ppm with six facial icons indicating indoor quality levels
• Calculates statistical weighted averages of TWA (8 hour Time Weighted Average) and STEL (15 minute Short Term Exposure Limit)

The Extech CO220 measures CO2 concentration, air temperature, and relative humidity, and will also calculate dew point and wet bulb temperatures. It includes a 99 Memory Datalogger for storing and retrieving readings with date and time stamping. This meter is shipped fully tested and calibrated and, with proper use, will provide years of reliable service.

Power the unit by plugging the AC adaptor into the meter and into an AC source. The meter will switch ON with a short beep.

The LCD will display the current CO2 concentration, air temperature, relative humidity, date, and time (date and time toggle every 10 seconds). Six facial icons indicate the indoor air quality level and appear on the top-tier display area. The facial icons are explained below.

The CO220 displays CO2 levels in PPM (parts per million) as well as with six, easy to follow facial icons. This chart shows each icon and its corresponding CO2 concentration level.

Time weighted average (TWA)

TWA is Time Weighted Average (8 hours); the meter updates the reading every 60 seconds. If the meter has been powered on for less than 8 hours, the TWA value will be the weighted average of readings taken since the unit was powered ON.

Short term exposure limit (STEL)

STEL is the Short-Term Exposure Limit (15 minutes weighted average); the meter updates readings every 60 seconds. If the meter has been powered on for less than 15 minutes, the STEL value shows the weighted average of reading taken since the unit was powered ON.

Datalogger memory - 99 readings

The user can store up to 99 CO2 readings with date/time stamp in memory for later recall. Once the memory is full, the meter will overwrite the first data point stored and continue to overwrite existing readings as new readings are stored.

Automatic Baseline (ABC) Calibration

ABC (Automatic Baseline Calibration) establishes a baseline calibration to eliminate the zero drift of the infrared sensor. The ABC function is always ON when the meter is ON. ABC is designed to calibrate the meter at the minimum CO2 reading detected during 7.5 days continuous monitoring (with power on). It assumes that the area being tested receives fresh air with a CO2 level of approximately 400ppm at some period of time during the seven days. It is not suitable to use desktop CO2 meters in closed areas with consistently high CO2 levels 24 hours a day.

1. CO2 reading

2. Relative Humidity Reading

3. Air Temperature Reading

4. Time/Date Display

5. SET button

6. ESC - MEM button

7. SELECT - RECALL button

8. C/F ‐ %RH button

9. CO2 button

10. AC adaptor jack

NOTE: CO2, Temperature and RH sensors on rear of instrument