Wastewater pumping stations
Levels at the wet well and in the kiosk, reported to the operator without a visit, and laid against pump runs and rainfall.
Hydrogen sulphide monitoring tag
The ZARC hydrogen sulphide tag reports the H2S concentration in the air, in parts per million and in real time, and alerts named people when it rises. Hydrogen sulphide, also spelled hydrogen sulfide, is the gas behind the rotten-egg smell of sewage and stagnant water. It drives odour complaints, eats concrete and electronics, and is dangerous at higher levels. The tag is complementary monitoring for sites where it forms.
01
What it reports
The tag reads hydrogen sulphide continuously 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.
Smell is no guide. The gas is obvious at very low levels, but the sense of smell fades as the concentration climbs, so the nose reports less just as the level becomes serious. A reading does not tire.
Most of the value is in the record. Hydrogen sulphide comes and goes with flow, temperature and how long sewage has sat, so a single visit proves little. A continuous trend shows when levels peak, how often, and whether dosing or ventilation has changed anything.
The same gas corrodes. It attacks concrete, copper and the electronics in control panels, so a persistent low level is a maintenance cost long before it is a safety question.
The tag is complementary monitoring; it does not replace certified gas detection. It is not a personal gas monitor, it is no part of a confined-space entry procedure, and it is not for use in zoned hazardous areas.
02
Applications
Hydrogen sulphide forms wherever organic matter breaks down without air. The uses below are the common ones.
Treatment works
Inlet works, sludge handling and odour control units, with a trend for each.
Odour complaints
A boundary record of when the gas was present and at what level, set against the times complaints were made.
Is the dosing working?
Chemical dosing is bought to keep hydrogen sulphide down. The trend before and after shows whether it does, and when a dosing pump has stopped.
Corrosion of control panels
A persistent level inside a kiosk or cabinet explains failing relays and blackened copper, and makes the case for sealing or ventilation.
Anaerobic digestion and biogas
Around digesters, gas handling and feedstock reception, as complementary monitoring beside the site's fixed detection.
Landfill and leachate
At leachate chambers and site boundaries.
Farms and slurry stores
Near slurry stores and reception pits, where the gas is released in bursts when slurry is stirred. The tag gives awareness and a record; it does not make a store safe to approach.
Food, rendering and paper
Processes and effluent plants that produce the gas as a by-product.
Drains, sumps and basements
Dry traps and stagnant sumps in buildings, found by the reading before the smell reaches the tenants.
03
Where it can go
The gas is heavier than air and collects low down and in enclosed spaces. Typical positions:
Kiosks and control cabinets
Inside the enclosure, where corrosion does its damage.
Above wet wells and chambers
Outside the zoned area, in the air people approach through.
Site boundaries
Facing the nearest neighbour, for the odour record.
Odour control units
At the outlet, to show the unit is working.
Plant buildings
At low level near sludge and effluent handling.
Basements and sumps
Near the drain or sump that is suspected.
04
In the dashboard
Every tag shows its live level and a trend from the last hour to the last year. The dashboard works out the maximum, minimum and average over any period, the time spent above each limit, and how often peaks occur, so a station that gasses every afternoon stands out from one that does so once a month. Records export for odour investigations, asset files and regulators.
Limits are set per tag: level, rate of rise and duration. 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 tag, grouped by site
- Trend graphs from one hour to one year
- Maximum, minimum and average over any period
- How often peaks occur, and when
- Time above each limit
- Before and after a change to dosing or ventilation
- Stations and sites compared side by side
- Every alert logged with the reading that raised it
- Records exported for odour investigations
- A tag that misses its reporting interval is flagged
05
Industries
Hydrogen sulphide tags are fitted wherever sewage, sludge or effluent is handled, including:
Energy and utilities
Pumping stations, treatment works and networks.
Critical national infrastructure
Water and wastewater assets.
Local government and public sector
Landfill, drainage and odour complaints.
Industrial and manufacturing
Effluent plants and process by-products.
Facilities management
Drains, sumps and plant in buildings.
Buildings and estates
Basements and drainage.
06
Technical specification
| Parameter | Specification |
|---|---|
| Measurement | Hydrogen sulphide concentration in air, read continuously and reported in real time |
| Gas | Hydrogen sulphide (H2S) |
| Units | ppm |
| Sensing | Electrochemical cell |
| 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 |
| 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, max/min/average, peak frequency, time above limits; 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, kiosk or boundary, outside zoned areas |
| Works alongside | Fixed gas detection and personal gas monitors |
| Not for | Personal gas monitoring, confined-space entry or zoned hazardous areas |
| 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 where the gas forms and what it is costing: complaints, corrosion or concern for people on site. That sets the positions.
Configuration
Tags are built to order with the range, reporting interval and limits agreed for each position.
Fitting
One fixing per tag and no cable, outside any zoned area. Nothing is connected to the site's control system.
Commissioning
A baseline is recorded over the first days, limits are set against it, and alert routes are tested.
Ready to get started? Every deployment begins with a site survey.
Book a site survey08
How it reports
Each reading leaves the tag on 433 MHz radio, reaches a ZARC gateway and appears on the dashboard, where limits are checked. The tag is transmit-only, with no receiver, and independent of the site's telemetry, so it adds a reading the control system does not have. The 433 MHz signal carries well out of kiosks and chambers where other radios struggle.
Related tags
Air quality
Ammonia and other odour compounds.
Tank level
Wet well and tank levels beside the gas reading.
Humidity
The damp that speeds corrosion.
Carbon monoxide (CO)
Where engines and fuel are the source.
Questions we answer most.
What does the hydrogen sulphide tag do?
It reports the H2S level in the air in ppm and alerts named people when it rises, with a full record over time.
Is hydrogen sulphide the same as hydrogen sulfide?
Yes. Sulphide is the UK spelling and sulfide the international one. The gas is H2S either way.
Can I rely on the smell instead?
No. The sense of smell fades as the level climbs, so smell is least reliable when the gas is most dangerous.
Can it help with odour complaints?
Yes. A boundary record shows when the gas was present and at what level, against the times complaints were made.
Can it show whether dosing is working?
Yes. The trend before and after a change shows the effect, and a rise shows when dosing has stopped.
Why monitor inside a control kiosk?
Hydrogen sulphide corrodes copper and electronics. A persistent level explains early failures and justifies sealing or ventilation.
Is it a personal gas monitor?
No. It does not replace personal gas monitors or fixed gas detection.
Can it be used for confined-space entry?
No. It is no part of a confined-space entry procedure.
Can it go in a zoned hazardous area?
No. The tag is fitted outside zoned hazardous areas.
What sensor does it use?
An electrochemical cell, supplied calibrated by the sensor manufacturer, with its life stated at order.
How is it powered?
By an internal battery lasting up to five years as standard, and longer where additional cells are fitted.
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.