Air quality monitoring for indoor aquatic facilities

Continuous trichloramine monitoring correlated with bather load and ventilation rates. 100% ARS compliance with 25% ventilation energy savings.

The context

Water and air are coupled systems

Indoor swimming pools generate chloramines — primarily trichloramine (NCl3) — from the reaction between chlorine disinfectants and organic matter introduced by bathers.

Chloramine production depends on water chemistry (free chlorine, pH, combined chlorine), bather load, water temperature and air exchange rate. Optimizing air quality requires understanding the complete system — not just measuring one parameter in isolation.

0.3 mg/m³

Regulatory NCl3 threshold set by the ARS — above this, eye and respiratory irritation occurs

40–60 %

Share of ventilation in the energy budget of an aquatic facility

x20

Bather load variation between Tuesday morning and Saturday afternoon

The challenge

Chloramines are invisible, dangerous, and energy-expensive to manage

The health risk

NCl3 concentrations above 0.3 mg/m3 cause eye and respiratory irritation. Chronic exposure affects lifeguards, swimming instructors and regular swimmers.

ARS regulations mandate monitoring. But in most aquatic facilities, measurements are spot-checks and manual — insufficient to detect peaks and prove continuous compliance.

The energy dilemma

Dilution ventilation remains the primary mitigation measure — but pool halls are large volumes requiring massive air exchange rates.

Running ventilation at maximum rate 24/7 is safe but financially and environmentally unsustainable. Bather load varies from 10 swimmers on Tuesday mornings to 200 families on Saturday — yet ventilation runs at a fixed rate.

How TERA 360 works

Correlated monitoring for intelligent ventilation

TERA 360 connects air quality, water quality, and bather load data to drive demand-based ventilation control.

Monitor the complete system

Trichloramine analyzers (Cylergie partnership), CO2/T/RH duct sensors (Modbus via ModLinkChainer), three-phase energy meters on AHUs, and occupancy sensors for bather load estimation. All connected to the Gateway Pure™ for a unified air + energy + occupancy view.

Correlate and predict

The platform builds a model linking bather load (from counting systems or CO2 proxy), water chemistry and ventilation rates to NCl3 concentrations. Predictive algorithms anticipate chloramine buildup and pre-adjust ventilation before levels approach regulatory thresholds.

Optimize ventilation

During low-occupancy periods, ventilation is reduced while maintaining NCl3 below 0.3 mg/m3. During high-occupancy periods, ventilation ramps up proactively based on the model. The result: ARS compliance maintained continuously with significantly lower energy consumption.

Sensors & systems

Measurement infrastructure for aquatic environments

Trichloramine analyzers (Cylergie)

Trichloramine sensors provided by our partner Cylergie, a strategic laboratory of the TERA Group. Positioned in the breathing zone. Regulatory threshold: 0.3 mg/m3. Connected via ModLinkChainer to the Gateway Pure™.

CO2/T/RH duct sensors

CO2 NDIR sensors (0-5000 ppm, Belimo, IP65), temperature and humidity in ducts — connected via Modbus through ModLinkChainer. CO2 serves as a proxy for bather load and ventilation effectiveness.

Water quality probes

pH, free chlorine, ORP/redox and combined chlorine monitoring at the pool return. Water temperature logged continuously. Data feeds into the chloramine production model.

Three-phase energy meter

Compact three-phase energy meter (Modbus RTU) connected via ModLinkChainer. Real-time AHU power consumption tracking. Precise quantification of savings from demand-based ventilation optimization.

TERA 360 swimming pool monitoring dashboard with NCl3 levels and ventilation status

Dashboards & alerts

Operational control for pool managers

Single-screen overview of all critical parameters: NCl3 level, water chemistry, ventilation rate, bather count and energy consumption.

Real-time status — NCl3 level with trend arrow and traffic-light indicators. Bather load profiles overlaid with NCl3 response curves.
ARS compliance — Percentage-of-time-in-compliance metrics. Daily, weekly and monthly reports auto-generated. Inspection-ready.
Energy analytics — Demand-based vs. fixed-rate baseline comparison. Seasonal patterns for budget forecasting.
Multi-level alerts — Advisory at 0.2 mg/m3, warning at 0.25 mg/m3, alarm at 0.3 mg/m3. SMS, email and on-screen notifications with acknowledgment tracking.

Benefits

Healthier air, lower costs, proven compliance

-25 %

Ventilation energy measured across deployed sites, without compromising air quality during peak bather loads.

100 %

ARS regulatory compliance maintained continuously. Complete audit trail for inspections.

Concrete results

Proactive ventilation management keeps NCl3 levels consistently low — not just below the regulatory threshold. Swimmers, lifeguards and staff benefit from measurably better air quality.

Correlation between water chemistry and air quality enables preventive action. When combined chlorine trends upward, operators are alerted to adjust water treatment before NCl3 rises — breaking the problem at its source.

100%

ARS compliance

25%

Energy savings