We said this already, but here at uRADMonitor, everything we learn in the field, every piece of user feedback, and every R&D result feeds into new products or upgrades: implementing better sensors, new connectivity options, and improvements that increase lifespan, robustness and accuracy. This is the direct result of our commitment to building the world’s largest Environmental Monitoring Network, a mission that can only be fulfilled through investment in quality and technology.

It’s now time to talk about the MODEL A4 again, this time announcing the new improvements in its new version , the 5th!

uRADMonitor MODEL A4

The uRADMonitor MODEL A4 is a fixed, automatic air quality monitoring station launched in late 2023, designed to track 11 environmental parameters simultaneously: including particulate matter (PM1, PM2.5, PM10), nitrogen dioxide, ozone, carbon monoxide, formaldehyde, CO₂, VOCs, temperature, and humidity , using 8 high-quality digital sensors housed in a weatherproof Stevenson Shield enclosure suitable for year-round outdoor use.

Built on a decade of community feedback, its most important feature is a modular design with a detachable sensor board that can be replaced easily in the field, even on pole-mounted installations, without requiring the unit to be brought back to a lab.
In 2025 the MODEL A4 received significant upgrades, including a reinforced steel-bar enclosure built to withstand direct impacts and a redesigned sensor board with a substantially improved NO2 sensor. Data is transmitted automatically over WiFi to the uRADMonitor cloud and is accessible in real time via the public API, making the A4 a practical and maintainable solution for both individual users and large-scale urban deployments such as the over 100 units installed across Bucharest’s Sector 1.

The 5th Version

The new version introduces several meaningful improvements. The particulate matter sensor has been upgraded to a larger, more robust unit – the same model used in the uRADMonitor MODEL A3, which has been independently lab-tested multiple times with excellent results. This means the A3’s proven PM accuracy is now directly available in the A4. The sensor also benefits from an extended operational lifespan, further enhanced by the A4’s duty-cycle management, which periodically pauses the internal fan to reduce wear and significantly prolong sensor life.

The VOC sensor now reports in micrograms per cubic meter instead of raw resistance values, making the data immediately interpretable without additional processing , a change our users have requested many times, and one that is long overdue.

As the model A4 connects via WIFI, we now report the signal strength in the data dashboard, offering additional insight on the connectivity performance of your unit.

As always, enjoy using our sensors as much as we enjoyed building them, and thank you for helping us grow the Global Environmental Monitoring Network : free, uncensored environmental data, available to everyone in real time.