The virus that instigates COVID-19 is quite the Goliath – and it has created mass awareness of the presence of contaminants in the air, with the menacing potential of severely affecting our health. It’s not just about the virus, though. The recent Lancet Commission WHO report has rung alarm bells the world over on the significant number of global deaths from air pollution. Indeed, air pollution is posing as quite an insurmountable hurdle for nations to cross to avert a socio-economic disaster. The WHO roadmap suggests an expansion of the knowledge base and efficient monitoring of air quality for a healthy world. This is easier said than done, due to the complex challenges associated with air quality monitoring and the enormous costs involved.

CHALLENGES WITH MONITORING IAQ

Biren Mahendra Shah

Today, the confusion is compounded with the advent of new entrants into the field, advocating low-cost sensors with lesser accuracies for indoor niche applications. In their current stage of development, electro-chemical sensors, photo ionisation detectors, optical particle counters and optical detectors can do only so much. The quality of the data is questionable when compared to the results from official monitoring stations carried out by conventional gas analyser monitoring stations, in accordance with international standards and methods. Indeed, many intrinsic constraints and limitations are associated with the existing low-cost solid-state sensors.

• Technically, the signals from sensors not only depend on the air pollutant of interest but also a combination of several effects, such as other interfering compounds, temperature, humidity, pressure and signal drift (instability of signal).
• At high concentrations, the signal from the air pollutant can be strong, but at ambient air levels, the signal is weak, in comparison to the interfering effects, and therefore the utility of the low-cost, solid-state sensors may be severely limited.
• Every type of pollutant gas, like Sox, Nox, CO2 and CO, requires an independent calibrated sensor. Similarly, different sensors are needed for temperature, air flow and humidity. Some vital monitoring of greenhouse gases, like methane, hydrogen sulphide and
ammonia, is generally neglected.
• These confluences of sensors call for regular maintenance and replacements.
• The area of coverage is limited, as a small volume of sample air is pumped into the solid-state sensors, thereby limiting the coverage by a maximum of five square metres of area.

PHOTONIC SENSING TECHNOLOGIES

A photonic system for monitoring IAQ brings the promise of higher accuracy with overarching capabilities for diverse applications. The uniqueness of photonic systems lies in an innovative application of the principles of laser back scattering, statistical mechanics, optoelectronics, artificial intelligence, machine/deep learning and the Internet of Things – resulting in a unique system capable of identification, classification and quantification of various pollutants simultaneously, with accuracies of less than one ppb, and of meteorological parameters with very high precision, sensitivity and accuracy.

The photonic system offers a number of merits over any of the currently available conventional methods. It typically has the following characteristics:
• It is portable, compact, low powered and economical.
• It is inherently a plug-and-play system, as such requiring no setting-up time and no additional civil infrastructure for housing.
• It provides information on all gases and meteorological parameters simultaneously

• It is a non-intrusive, remote, real-time monitoring system with very high sensitivities and accuracies.
• It is a single system capable of monitoring in both spatial and temporal domains, with high sampling rates.
• The area it covers ranges from one metre to 1,000 metres in radius. The unit can be rotated 360 degrees. The data of air can be collected vertically as well as horizontally.
• The laser beam travels to the targeted area and assists in identifying the source of pollutants.
• Above all, the system requires no routine calibration.

The system has embedded intelligent algorithms and software operating on a user-selectable remote server with data encryption, ensuring data security and free flow of desired information to authorised users, as per specific requirements. Besides monitoring a wide range of gases; ambient temperature; humidity; air flow parameters, like speed, velocity and direction; precipitation and solar radiation, the photonic system is able to identify bacteria in the air, given the fact that conventionally, random sample volume of air is taken periodically, and it is only by a stroke of luck that one is able to capture the bacteria in the air.

Monitoring is associated with using consumables for collecting samples, incubating, waiting for microbial growth to occur, discriminating the type, and counting the colony. The complete process takes 3-5 days. And unless sterilisation/fumigation is done in the space, the gram-negative bacteria would spread, infect and do severe damage.

Photonic Sensing is a breakthrough methodology to monitor in situ (real-time) bacteria, viruses, fungi and all types of harmful pathogens in the air. It is a powerful monitoring device that can make the detection process of important clinical bacteria and virus simple, quick and effective by sensing relevant parameters that can be related to infectious processes.

Hence, it counters the limitations of conventional systems through:
• Monitoring in real-time
• Scanning 24x7x365 every metre of the space, and high sampling frequency
• Identifying the geo-location
• Validating qualification and quantification of bacteria
• Avoiding retesting, hence saving time
• Reducing the dependence on outside service
Photonic Sensing technology currently detects the following bacteria that generally lead to 80% of infections…
• Staphylococcus aureus
• Escherichia coli
• Klebsiella pneumoniae
• Pseudomonas aeruginosa
• Enterococcus faecalis
• Stenotrophomonas maltophilia
• Staphylococcus saprophyticus

CONCLUSION

Photonic systems provide real-time insights, alerts and longer-term perspectives on how conditions change in the indoor space. Their implementation for indoor monitoring is not complex or remarkably expensive. They can create value in monitoring, modelling and forecasting indoor information, and in interpreting and communicating in real-time in a form that decision-makers can use.