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Evaluating Carbon Dioxide Data Loggers – 5 Important Considerations

Smart wireless technology provides benefits including efficient data collection, easy management with data sharing, and overall user-friendly operation. PHOTO CREDIT: Onset

People spend a significant amount of their time indoors, including interior environments such as office buildings, schools, hospitals and other commercial spaces, underscoring the importance of maintaining suitable indoor air quality (IAQ) in these enclosed settings. The potential health liability associated with interior air pollution has been stressed by the U.S. Environmental Protection Agency (EPA), which identified IAQ as one of the top five most urgent environmental risks to public health.

With these concerns in mind, adequate ventilation in buildings is vital for ensuring that proper IAQ conditions are maintained. Heating, ventilation, and air conditioning (HVAC) systems are crucial in this regard and serve an important role by circulating air, replenishing interiors with outdoor air and oxygen, and expelling stale air, carbon dioxide (CO2), moisture and pollutants to the outside.

Building managers and engineers typically have the responsibility of overseeing these systems, as well as verifying that HVAC equipment is running efficiently and properly ventilating building spaces. To measure ventilation performance, interior CO2 levels can be monitored to determine if an HVAC system is moving a sufficient amount of air into and through the building. The concentration of CO2 in an occupied indoor space indicates if the building’s air exchange balance is appropriate and if an optimal amount of outside air is being mixed with air that has been circulating in the building.

Monitoring CO2 levels can also serve as a relatively easy-to-measure surrogate for indoor pollutants emitted by humans and as a general indicator for a building’s IAQ. In buildings with subpar ventilating systems, CO2 concentrations and other pollutants can accumulate. When interior CO2 levels become unusually high, occupants can become drowsy, suffer from headaches, or function at lower activity levels.

According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), indoor CO2 concentrations should not exceed outdoor CO2 amounts by over 600 ppm. Additionally, the National Institute for Occupational Safety and Health regards indoor CO2 levels higher than 1,000 ppm as a marker indicating inadequate ventilation. Data on CO2 levels and the effects of increased concentrations on healthy adults are highlighted below:

Normal outdoor levels: 350 - 450 ppm
Acceptable indoor levels: < 600 ppm
Complaints of stuffiness and odors: 600 - 1000 ppm
ASHRAE and OSHA standards: 1000 ppm
General drowsiness: 1000 - 2500 ppm
Adverse health effects expected: 2500 - 5000 ppm
Maximum allowed concentration within an 8 hour working period: 5000 ppm  

By conducting a CO2 monitoring program, building operators can be armed with information that supports better decisions in terms of ventilation control and HVAC upgrades – projects which can lead to significant energy savings and improved overall indoor quality. Comprehensive and location-specific CO2 data in building environments can also help guide HVAC improvements in terms of implementing the most effective and cost-efficient solutions.

Fortunately, indoor CO2 concentrations can be easily measured by battery-powered CO2 data loggers. These compact, handheld devices – roughly the same size and shape as a wall-mounted home thermostat – can be installed anywhere throughout a building where CO2 data is needed. Measurements are typically provided over a range of 0 – 5,000 parts per million (PPM) and today’s newer options enable users to access data from mobile devices and quickly download data directly to a laptop or the cloud.

When researching available CO2 data loggers on the market, check for certain key elements that should factor into the decision-making process, such as:

1. Bluetooth Compatibility

When evaluating the range of available CO2 data loggers, an important consideration is the inclusion of smart technology which can provide unprecedented benefits in terms of efficient data collection and management and user-friendly operation. Leveraging today’s latest advancements in wireless communication, certain CO2 data loggers now incorporate Bluetooth Low Energy (BLE) technology that allows data to be retrieved faster and more conveniently than ever before.

A BLE-equipped CO2 data logger offers the capacity to record and transmit wirelessly to mobile devices, enabling users to access measurements from the logger remotely within a 100-foot range. By eliminating the need to log on to the internet, pair devices, install computer software, or connect the logger to a computer for downloading data, building managers can decrease the time and costs associated with CO2 monitoring programs and streamline indoor air quality studies.

BLE data loggers can be particularly advantageous in buildings where multiple CO2 data loggers are employed or in applications where physically downloading data from the logger is difficult, such as ventilation system monitoring.

2. Automatic Calibration

To ensure the accuracy of the information received, CO2 data loggers need to be calibrated to reduce bias in readings and guarantee that measurable data is valid. A CO2 data logger should come equipped with a relatively easy and straightforward process for calibrating the instrument for maximum precision in conducting measurements. 

When assessing calibration features, look for products that offer both manual and automatic calibration methods, which provides the most assurance for timely calibrations. Manual calibration, which is typically the most accurate calibration method, commonly uses outside air at 400 ppm as a baseline. Users should perform a manual calibration prior to the first deployment to ensure that the initial readings are relevant.

Products offering both calibration methods will typically auto-calibrate after a specified time period if a manual calibration is not performed. The automatic calibration (for products that are based on 400 ppm) assume that the CO2 data logger will encounter 400 ppm at some point during its measurement cycle, which is a common occurrence in many schools, hospitals and office buildings, especially during nights or over the weekends.

In choosing the most effective option, another important consideration are CO2 data loggers that feature non-dispersive infrared (NDIR) CO2 sensor technology. NDIR represents the latest technology available for low-cost, low-power CO2 sensing and offers performance benefits related to accuracy and long-term stability. Additionally, NDIR technology supports recalibrations without the need for calibration gas.

3. LCD Display with Alarm Notifications

Building managers should also look for a CO2 data logger that features an LCD display with alarm notifications.

An LCD display will deliver quick and concise information depicting current CO2 levels, logging status, battery use, memory consumption, as well as other categories and levels. Users with little time to waste can appreciate the time-efficient benefit of working with a screen that is both distinct and responsive.

With alarm notification capabilities, a CO2 data logger will issue an audible alert and display a visual warning on its LCD screen in the event of a problem, such as if CO2 concentrations in a building exceed a set threshold.

When evaluating CO2 data loggers with this feature, consider products that include fast and simple alarm enabling. Look for options that provide both audible and display alarm notifications so that building managers can be alerted to problems as soon as possible, allowing for the most efficient corrective action.

4. Long Battery Life

The availability of a long-life battery is an additional important factor to consider in evaluating and comparing CO2 data loggers.

While most products on the market can only run for a short time on battery power or require a very expensive battery, options are now available that allow for 6-month continuous logging operations. By utilizing a CO2 data logger with a longer-term battery life, users can benefit from the flexibility afforded by increased spatial coverage and the ability to set up CO2 monitoring in locations where no AC power is available, including in or near air ducts.

5. USB Capabilities

Finally, when choosing a CO2 data logger, the availability of a USB port is another key element to take into account. USB ports offer the advantage of flexibility in terms of how data is accessed and analyzed. Through a USB port, users can connect a CO2 data logger directly to a computer running graphing and analysis software, enabling users to quickly plot, analyze and extract data or create visual presentations.  

A USB port also offers the advantage of greater versatility with regard to power options, allowing for a higher number of application scenarios. Specifically, this includes the capacity for an off-the-shelf USB charger to power the CO2 data logger for longer deployments or if faster LCD refresh rates/alarm responses are required, which would normally use battery life at a quicker speed.

Greg Lowitz is the founder and CEO of Buildera. He can be reached via his company website at: www.buildera.com. Special thanks to Onset for providing images for this story.

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