Why CT4CA Exists

The coalition launched roughly six months before the deadline for EU Member States to transpose the revised Ambient Air Quality Directive (AAQD, Directive 2024/2881) into national law . The AAQD sets significantly stricter limit values for PM2.5, PM10, and NO₂ starting in 2030, aiming to progressively align EU standards with World Health Organization (WHO) Air Quality Guidelines . CT4CA's core argument is that these ambitious targets can only be met if authorities have high-resolution, locally actionable data — and that high-quality small sensors are the most practical way to deliver that data .

Air pollution remains the number one environmental cause of premature death in Europe, and CT4CA members argue that citizens cannot wait until the extended 2035–2040 deadlines to breathe clean air .

The Three Core Goals

CT4CA has three primary objectives:

1. Secure formal recognition of high-quality small sensor systems in the EU's revised AAQD and its upcoming Implementing Acts — the technical rules that will define data quality objectives, modelling requirements, and spatial representativeness criteria .
2. Provide technical expertise to EU policymakers — the European Commission and European Parliament — as Member States race to transpose the new stricter limits .
3. Promote a shift toward higher-resolution, locally representative air quality data that can guide more targeted pollution reduction policies .

The coalition's motto is "Cleaner air starts with better information" .

How Small Sensors Complement Fixed Monitoring Stations

The coalition is clear that regulatory reference stations remain the backbone of official air quality monitoring and will not be replaced . However, they argue these stations alone have significant gaps:

Air pollution is highly localized — pollutant concentrations can change dramatically over just a few hundred meters depending on road traffic, industrial activity, port/airport operations, weather, and urban layout . Fixed stations miss these micro-variations.

Small sensor networks help authorities:

• Identify pollution hotspots at street, school, and neighborhood level that reference stations might miss
• Improve spatial representativeness of the overall monitoring network
• Provide near-real-time data to track pollution events as they happen
• Assess the effectiveness of local action plans (e.g., low-emission zones, traffic restrictions)
• Better protect vulnerable populations by identifying the most exposed areas

What CT4CA Is Asking For

The coalition is calling on the European Commission to formally recognize high-quality small sensors in the Implementing Acts that will define technical requirements for modelling, spatial representativeness, data quality objectives, and indicative measurements . CT4CA emphasizes it does not aim to promote any one company or technology, but rather to defend the principle that small sensors deserve a recognized role in the EU's clean air framework . The coalition states that European technical specifications already exist to enable sensor deployment today, and that greater acceptance of reliable sensor data by public authorities would enable more targeted and responsive clean air action .

Why CT4CA Exists

The coalition launched roughly six months before the deadline for EU Member States to transpose the revised Ambient Air Quality Directive (AAQD, Directive 2024/2881) into national law . The AAQD sets significantly stricter limit values for PM2.5, PM10, and NO₂ starting in 2030, aiming to progressively align EU standards with World Health Organization (WHO) Air Quality Guidelines . CT4CA's core argument is that these ambitious targets can only be met if authorities have high-resolution, locally actionable data — and that high-quality small sensors are the most practical way to deliver that data .

Air pollution remains the number one environmental cause of premature death in Europe, and CT4CA members argue that citizens cannot wait until the extended 2035–2040 deadlines to breathe clean air .

The Three Core Goals

CT4CA has three primary objectives:

1. Secure formal recognition of high-quality small sensor systems in the EU's revised AAQD and its upcoming Implementing Acts — the technical rules that will define data quality objectives, modelling requirements, and spatial representativeness criteria .
2. Provide technical expertise to EU policymakers — the European Commission and European Parliament — as Member States race to transpose the new stricter limits .
3. Promote a shift toward higher-resolution, locally representative air quality data that can guide more targeted pollution reduction policies .

The coalition's motto is "Cleaner air starts with better information" .

How Small Sensors Complement Fixed Monitoring Stations

The coalition is clear that regulatory reference stations remain the backbone of official air quality monitoring and will not be replaced . However, they argue these stations alone have significant gaps:

Air pollution is highly localized — pollutant concentrations can change dramatically over just a few hundred meters depending on road traffic, industrial activity, port/airport operations, weather, and urban layout . Fixed stations miss these micro-variations.

Small sensor networks help authorities:

• Identify pollution hotspots at street, school, and neighborhood level that reference stations might miss
• Improve spatial representativeness of the overall monitoring network
• Provide near-real-time data to track pollution events as they happen
• Assess the effectiveness of local action plans (e.g., low-emission zones, traffic restrictions)
• Better protect vulnerable populations by identifying the most exposed areas

What CT4CA Is Asking For

The coalition is calling on the European Commission to formally recognize high-quality small sensors in the Implementing Acts that will define technical requirements for modelling, spatial representativeness, data quality objectives, and indicative measurements . CT4CA emphasizes it does not aim to promote any one company or technology, but rather to defend the principle that small sensors deserve a recognized role in the EU's clean air framework . The coalition states that European technical specifications already exist to enable sensor deployment today, and that greater acceptance of reliable sensor data by public authorities would enable more targeted and responsive clean air action .