C-21 VOC Gas Sensor

EcoSensors C-21 VOC Sensor is a versatile and easy to to use VOC detector.  Handheld with integrated battery or wall mount with audible alarm  Internal relays and voltage output to use for control or data logging.

VOC Information

3 In Stock

The model C‑21 is a solid‑state gas monitor capable of sensing a variety of gases and vapors. The ones it is generally sensitive to are called VOCS (volatile organic compounds), and the most common application of the C‑21 is for solvent vapors. Common examples are paint thinners, dry cleaning fluids, cleaning solvents, and gasoline vapors. The instrument does not respond to carbon dioxide or radon, and has only a weak response to carbon monoxide. The C‑21 is self‑contained except for its AC adapter power module. The instrument also has an audio alarm and has outputs to external alarms, data loggers, calibration equipment, etc.


     -Constantly monitors your work environment

     -Detects leaks and poor air quality before they are a health hazard

     -Alarms below OSHA TLV for most common solvent-based VOCs

     -No installation. Easily used and understood by non-technical personnel

     -Virtually no maintenance


     -Integrated battery allows for portable use

     -Internal audible alarm

     -Internal control relays - user settable

     -Highly sensitive to solvent vapors and other VOCs. Bright green-yellow-red display clearly shows hazard level of gas or vapor.

     -Detects down to OSHA, EPA, and other regulatory-mandated levels...typically at low ppm concentrations.

     -Has built-in rechargeable battery for portable use in tracking

     -Rugged construction with many safety features

     -Virtually no maintenance

What comes with the C-21:

     -C-21 VOC Monitor

     -AC Adapter

     -Magnetic strip for mounting to metal surfaces easily

     -User Manual

     -Calibration Certificate

C-21 VOC Sensor Package


Typical Detection Levels of C-21:

The C-21 will detect different levels of VOC's differently, below is a summary chart showing some of the VOC detection limits

VOC Gasses                 


Detection Limit      


Detection Range    

Alarm (first red bar)      
Acetone 4-5 ppm 30 ppm 20-25 ppm 750 ppm
Benzene 5-10 ppm 60 ppm 25-50 ppm 10 ppm
Diacetone Alcohol 5-10 ppm 60 ppm 25-50 ppm 50 ppm
Formaldehyde 1-5 ppm 30 ppm 15-25 ppm 0.1 ppm
Methylene Chloride 8-10 ppm 60 ppm 40-50 ppm 50 ppm
Perchloroethylene 5 ppm 60 ppm 50 ppm 50 ppm
Toluene 3-5 ppm 30 ppm 15-25 ppm 50 ppm
Trichloroethylene 10-20 ppm 150 ppm 50-100 ppm 50 ppm

 * Threshold Limit Value (TLV).   Average estimate of government industrial hygienists for repeated worker exposure.


C-21 as a relay controller:

The C-21 VOC sensor can be used as a controller for external alarms, vent fans, or other devices.  An integrated relay rated for up to 30 Volts at 130 mA will change states at the alarm level set by the customer.  Dip switches in the rear of the device can be set to change the alarm state based on specific application needs.  Also, dip switches will allow audible alarm to be turned ON or OFF.  See image below for visual reference of rear of the C-21.

 C-21 VOC Sensor user settings

Also shown is the replaceable battery in the C-21.  A simple plug in and to battery is included for replacement if it ever becomes necessary.


Data Logging:

Data logging with the C-21 VOC Sensor is possible with an external data logger such as the DL-4C and DL-4V.  Using the 0-2 vdc output signal from the C-21, the DL-4C or DL-4V can log and save gas measurements. 





Links to Tech tips and Info:

VOC Information

C-21 VOC Sensor Set-Point Adjustment

C-21 VOC Sensor Application in Dry Cleaning

C-21 VOC Sensor Responsiveness to specific VOC's

C-21 VOC Sensor Calibration Instructions

C-21 VOC Sensor user notes and considerations

C-21 VOC detection  ranges measured by C-21sensor

SE-4 Replacement Sensor

 C-21 Accessories
Intro video on the C-21 VOC Monitor

More Information
Manufacturer Eco Sensors
Quickbooks Stock Level 3.000000
Call For Price No
Resolution Green = normal. Yellow = caution. Red = danger.
Response Time Within a few seconds of the VOC gas reaching the sensor
Sensor type HMOS (heated metal oxide semiconductor) sensor
Sampling Method Diffusion
Operation Modes Battery, and AC Power
Operational Temperature Range 32-105 F
Operational RH Range 15-85% RH, non-condensing
Power Requirements Self-contained NiCad or NiMH. Approximately 2 hour capacity. Recharged by AC adapter overnight.
Size 85 × 35 × 60 mm (3.25 × 1.375 × 2.375 in)
Field Replaceable Battery No
Warranty 1 Year
Audible Alarm Yes
Calibration Annually
Sensor Life 2 Years
Range Full scale = 50-100 ppm for most solvent based VOCs
Unit Features

-Constantly Monitor Work Environment

-Early Leak Detection

-Extreme Ease of Use

-Virtually No Maintenance                                  

Sensor Range

VOC Level Dependent

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