Classrooms and lecture rooms
The reading rises with every occupied hour in a room that is under-ventilated. The dashboard shows which rooms need windows opened, plant adjusted or occupancy changed.
Carbon dioxide monitoring tag
The ZARC carbon dioxide tag reports the CO2 concentration in a space, in parts per million and in real time, and alerts when it passes a limit you set. In occupied rooms it is the plain measure of ventilation: people breathe out CO2, so the reading rises when fresh air is not keeping up. In cellars, gas stores and growing rooms it shows a build-up from a cylinder, a process or a crop. It runs on its own battery and needs no wiring.
01
What it reports
The tag reads CO2 continuously by infrared sensing and reports in parts per million at the interval set for the site, down to every minute. Each report can carry the current level and the maximum, minimum and average for the interval.
Outdoor air sits at around 400 ppm. Health and Safety Executive guidance treats a reading consistently below 800 ppm in an occupied room as a sign of good ventilation, and one consistently above 1,500 ppm as a sign of poor ventilation that needs action. The same guidance is clear that CO2 is a broad guide to ventilation, not a safe level.
The value is in the pattern. A classroom that climbs past 1,500 ppm by mid-morning every day, or a meeting room that never recovers between bookings, is a ventilation problem with evidence attached.
Where CO2 comes from a cylinder or a process, the tag reports a build-up as a rising level. In those places it is complementary monitoring; it does not replace certified gas detection where a risk assessment or a standard requires it.
02
Applications
Carbon dioxide answers one question in occupied rooms and a different one where the gas is stored or made. The uses below are the common ones.
Offices and meeting rooms
Stuffy rooms measured, not argued about. Levels through the day show where ventilation falls short of the people using the space.
Ventilation that is not working
A room that used to hold 700 ppm and now reaches 1,400 has lost airflow: a failed fan, a closed damper or a blocked filter.
Energy against fresh air
Ventilation costs heat. The CO2 record shows where a building is over-ventilated when empty and under-ventilated when full, so plant runs to need.
Cellars and drinks gas stores
Cylinders and dispense lines leak, and the gas collects low down. A rising level is reported to people who are not in the cellar. Complementary to the fixed CO2 safety monitor a cellar should already have.
Dry ice and cold chain
Stores and vehicles where dry ice is used give off CO2 as it warms. The tag reports the level beside the temperature.
Growing rooms and glasshouses
CO2 is dosed to feed a crop. The tag shows the level held and when dosing has stopped or overrun.
Care homes and wards
Fresh air in rooms where people spend the whole day.
Occupancy from the air
CO2 follows the number of people in a room, so the trend shows how spaces are really used, without a camera and without identifying anyone.
After a refit
A before-and-after record that new ventilation delivers what was specified.
03
Where it can go
Where the tag sits decides what the reading means. Typical positions:
At head height in occupied rooms
On a wall, more than half a metre from where people sit, away from windows and supply grilles.
One per room
In each classroom, office or meeting room to be compared.
Low down in cellars and stores
CO2 is heavier than air and collects at floor level.
Beside cylinders and dispense equipment
Near the likely source of a leak.
In growing areas
At crop height, away from the dosing outlet.
In return air
At an extract grille, for the average of a larger space.
04
In the dashboard
Every tag shows its live CO2 level and a trend from the last hour to the last year. The dashboard works out the average over the occupied period, the daily peak and the time spent above each limit, and sets rooms side by side so the worst-ventilated are obvious. Records export for ventilation surveys, risk assessments and reports to governors, landlords or tenants.
Limits are set per tag: level, rate of rise and duration, with different values for occupied hours where needed. When one is crossed the alert is raised in real time and goes by email or SMS, and through an app where required, to the people you name, with escalation to further contacts.
- Live ppm for every room and store
- Average over the occupied period
- Daily peak and when it happened
- Time above 800 ppm, 1,500 ppm or your own limits
- Rooms and buildings ranked side by side
- Trend graphs from one hour to one year
- Patterns by time of day and day of week
- Every alert logged with the reading that raised it
- Records exported for surveys and risk assessments
- A tag that misses its reporting interval is flagged
05
Industries
Carbon dioxide tags are fitted wherever people share air or the gas is stored, including:
Local government and public sector
Schools, colleges, libraries and offices.
Facilities management
Ventilation performance across a portfolio.
Buildings and estates
Offices, meeting rooms and common areas.
Healthcare
Wards, waiting rooms and care settings.
Industrial and manufacturing
Processes and stores that use the gas.
Logistics and supply chain
Cold chain stores using dry ice.
06
Technical specification
| Parameter | Specification |
|---|---|
| Measurement | Carbon dioxide concentration in air, read continuously and reported in real time |
| Gas | Carbon dioxide (CO2) |
| Units | ppm |
| Sensing | Non-dispersive infrared (NDIR), the type recommended for ventilation monitoring |
| Values reported | Current level, maximum, minimum and average for each reporting interval |
| Range and accuracy | Specified to the requirement |
| Calibration | Sensors supplied calibrated by the sensor manufacturer |
| Sensor life | Stated for the sensor fitted; replacement planned at order |
| Reporting interval | Configurable, down to every minute |
| Limit alerts | Level above a limit you set |
| Trend alerts | Level rising at a rate you set |
| Duration alerts | Time above a limit, so a brief peak does not alarm |
| Occupied-hours limits | Separate limits for occupied and empty periods |
| Alert delivery | Dashboard, email or SMS; app where required |
| Recipients | Named people and groups, with escalation to further contacts |
| Missed reports | A tag that misses its reporting interval is flagged in the dashboard |
| Gateway power loss | Raises its own platform alert |
| Dashboard | Live level, trends, occupied-period average, daily peak, time above limits, rooms compared; configured to your requirement |
| Records | Every reading and alert time-stamped and exportable |
| Data | Full reading history; UK-hosted or on servers on your own site |
| Power | Internal battery, up to five years as standard; longer with additional cells |
| Radio | 433 MHz, one-way (transmit only) |
| Radio range | Site-dependent; confirmed by site survey |
| Environment | Indoor or outdoor, enclosure specified to the location |
| Enclosure | Vented to the air it samples; standard or built to the site |
| Mounting | Wall at head height in rooms; low level in cellars and stores |
| Not for | Life-safety gas detection where a standard or risk assessment requires a certified detector |
| Charges | No per-alert, per-user or licence charges |
| Manufacture | Made to order in the UK |
| Certification | CE marked |
07
From requirement to live alerts
Requirement
Tell us which rooms or stores matter and why: ventilation, a stored gas or a process. That sets the positions and the limits.
Configuration
Tags are built to order with the range, reporting interval and limits for each space.
Fitting
One fixing per tag, at the height that suits the use. No cable and no connection to the ventilation plant.
Commissioning
Readings are checked in an empty room and a full one, limits are set, and alert routes are tested.
Ready to get started? Every deployment begins with a site survey.
Book a site survey08
How it reports
Readings travel over 433 MHz radio from the tag to a ZARC gateway, and from the gateway to the dashboard, where limits are checked. The tag only transmits; it has no receiver. Because it needs no wiring, a tag can be moved from room to room to survey a building before permanent positions are chosen.
Related tags
Air quality
Particulates and vapours in the same air.
Carbon monoxide (CO)
Where fuel is burned or engines run.
Temperature
Comfort and heat loss beside ventilation.
Humidity
Moisture that poor ventilation leaves behind.
Questions we answer most.
What does a CO2 reading tell me about a room?
Whether ventilation is keeping up with the people in it. People breathe out CO2, so the level rises when fresh air falls short.
What is a good CO2 level indoors?
HSE guidance treats a reading consistently below 800 ppm as a sign of good ventilation and one consistently above 1,500 ppm as a sign of poor ventilation. It is a broad guide, not a safe level.
What is the CO2 level outdoors?
Around 400 ppm.
What type of sensor does the tag use?
Non-dispersive infrared (NDIR), the type recommended for ventilation monitoring.
Where should the tag be placed in a room?
At head height, more than half a metre from people, and away from windows, doors and supply grilles.
Can it monitor a cellar or gas store?
Yes, as complementary monitoring. It does not replace the fixed CO2 safety monitor a cellar or store should already have.
Can it show how a room is used?
Yes. CO2 follows the number of people present, so the trend shows occupancy without a camera.
Does it need power or a network?
No. It runs on an internal battery and reports by radio to a ZARC gateway.
How long does the battery last?
Up to five years as standard, and longer where additional cells are fitted.
Can tags be moved between rooms?
Yes. There is no wiring, so a tag can survey several rooms before a permanent position is chosen.
Is it a certified gas detector?
No. It is complementary monitoring and does not replace certified gas detection.
Looking for something else?
We work with any sensor for any application.
Most sensing needs are met by a tag we already build, configured for your equipment. If yours needs a sensor or interface we don't list, we have the engineering to build it. Tell us what you need to measure, and we will tell you how we would do it.
Discuss your requirementDiscuss a monitoring
or alerting solution
Tell us what is happening on site, what you need to see, and the event you need to hear about. We will come back with the system that answers it.
Direct contact
Location
Venator House, Unit 9, 15-17 St Stephen's Road, Bournemouth
Dorset, BH2 6LA · VAT GB 409644484
Products contact
Contact the engineering team
Direct to the team that designs and builds the range. Tell us the equipment and the event that matters.