Air Quality Assurance: Calibrating Monitors For Reliable Data

Calibration is the process of configuring a device to match a known standard. For air quality monitors, calibration ensures that the device is providing accurate readings of the air quality. The frequency of calibration depends on the type of device, usage patterns, and specific requirements or guidelines. For example, the Occupational Safety and Health Administration (OSHA) recommends calibrating gas detectors before each use, while some manufacturers of air quality monitors suggest calibration every 6 months. Calibration methods can be manual or automated, with the latter being more suitable for a large number of devices. The calibration process typically involves exposing the device to a known concentration of test gas and adjusting its sensors accordingly.

Manual calibration of air monitors

Manual calibration of air quality monitors is a straightforward process that can be performed by following a few simple steps. Firstly, place two air quality monitors side by side, maintaining a distance of approximately 25 cm between them. Ensure that the room in which the calibration is being conducted is well-ventilated. Then, access the settings of the monitors by navigating to "Advanced Parameters" and selecting the specific monitor to be calibrated. From there, proceed to the "Advanced" section and initiate the calibration process. It is important to note that this process may take around 8 hours to complete.

During the calibration, the monitors will compare their readings and make adjustments to ensure they are aligned. This process is known as a "bump test" and is used to verify the accuracy of the sensors. If the readings on the monitors differ significantly, a full calibration is required. This involves reconfiguring the sensors and adjusting the readings to match the contents of a test gas cylinder.

It is worth noting that the precision of air quality monitors can vary, and a difference of up to 100ppm between two monitors is considered acceptable. Additionally, the temperature calibration of the monitors can be fine-tuned using an external reference, such as a thermometer, by calculating the average temperature between the monitor and the reference source.

Manual calibration is particularly useful when monitors are not used regularly. It ensures that the devices are functioning correctly and provides reliable readings. However, if you use your monitors frequently or have a large number of devices to calibrate, an automated calibration system may be more efficient.

Automated calibration systems

The Draeger X-am Bump Test and Calibration Station is a simple, electricity-free option. The 4-Gas cylinder screws in, and the system is ready when a monitor is plugged in. This system is designed for individual monitors and cannot be expanded.

The MicroDock II Docking Station and the RKI Instruments SDM-2009 Calibration Station are other examples of automated calibration systems. They are designed to fit specific monitor models.

The AQM 65 is another example of an automated calibration system. It is a compact ambient air quality monitoring system that can measure up to 20 gaseous and particulate pollutants and environmental parameters simultaneously. It offers a fully integrated calibration system, which enables the automatic scheduling of calibrations, saving time and money. The AQM 65 is supported by a global distribution network, providing easy access to skilled technicians and spare parts.

Calibration intervals

For air monitors that are used infrequently, such as every 30 days or less, it is recommended to calibrate each time before use to ensure accurate results. This can be done manually, which takes around 5 minutes per monitor, or through an automated system that can calibrate multiple monitors overnight or when not in use.

For air monitors that are used frequently, such as daily, calibration can be done less often, such as every 4-6 months. However, to ensure the devices are registering accurately, bump testing should be conducted more frequently, such as every couple of weeks.

Automated calibration systems, such as docking stations, can simplify the process by automatically calibrating monitors when they are not in use. These systems can also perform bump tests, which verify the calibration of the monitor by exposing it to a known concentration of test gas.

In addition to the frequency of use, environmental conditions can also impact calibration intervals. Sensors should be calibrated in environmental conditions that match or are similar to the actual workplace conditions, as responsiveness can vary with temperature and humidity.

It is important to follow standard procedures for regular calibration and keep calibration records for the life of each instrument. This helps ensure accurate readings, identify monitors with a history of maintenance issues, and track sensor drift to determine when sensors need replacement.

Calibration gas

The calibration gas must be certified and traceable to the National Institute of Standards and Technology (NIST) to ensure accuracy. It is important to use the correct calibration gas recommended by the manufacturer, as impure or incorrect calibration gas can lead to inaccurate measurements and compromise the safety of the device. The environment in which the calibration takes place can also impact the results, so it is recommended to calibrate the monitors in similar conditions to their working environment, such as temperature, pressure, and humidity.

The calibration process for smart indoor air quality monitors may vary slightly. For example, some monitors require placement in a well-ventilated room and adjustment of settings through an application. The calibration procedure for these monitors can take around 8 hours.

The frequency of calibration depends on the specific device and usage patterns. While it is ideal to calibrate before each use, this may not be practical for teams with many monitors. In such cases, it is recommended to follow the manufacturer's guidelines, perform bump tests regularly, and conduct full calibrations when necessary.

Calibration services

Mobile Calibration Services LLC offers a portable and fixed system calibration service for air monitors. Their technicians are trained on various air monitors on the market and have studied each manufacturer's manuals. With over 30 years of calibration experience, they provide regular scheduled calibrations to ensure monitor readiness, sensor accuracy, employee safety, and compliance with governmental regulations.

OSHA provides guidelines and recommendations for calibrating direct-reading portable gas monitors (DRPGMs) to protect workers from hazardous gases in the workplace. They advise following the manufacturer's recommendations and developing standard procedures for calibration and usage. OSHA also emphasises the importance of proper maintenance and calibration to ensure the accuracy of gas monitors.

Aeroqual offers the AQM 65 Air Monitoring Station, which includes an integrated calibration system. This system enables automatic scheduling of calibrations, saving time and money. The AQM 65 can measure multiple air pollutants and environmental parameters simultaneously and is suitable for various projects, including national and urban air monitoring.

PK Safety Supply provides resources and services related to gas detector calibration. They offer guidance on how often to calibrate gas detectors and the different methods available, such as bump testing and full calibration. PK Safety also provides a gas detector calibration service to assist companies in ensuring the accuracy and reliability of their equipment.

Overall, calibration services play a crucial role in maintaining the accuracy and reliability of air quality monitoring equipment. By utilising these services, companies can ensure the safety of their workers and compliance with relevant regulations. Regular calibration helps to identify any issues with the equipment and ensures that data collected is accurate and reliable.

Frequently asked questions