Floating hood for greenhouse gas monitoring at wastewater treatment plants

Gas Dome 300

The floating PVC hood captures nitrous oxide (N₂O), methane (CH₄) and CO₂ directly above the basin — a solid data foundation for your greenhouse gas inventory and compatible with any Fresenius gas analyzer.

  • CH₄ Methane GWP 28× CO₂
  • N₂O Nitrous oxide GWP 273× CO₂
  • CO₂ Carbon dioxide Reference
Gas Dome 300 – Floating hood for greenhouse gas monitoring at wastewater treatment plants
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The Product

Floating PVC hood for direct capture of nitrous oxide, methane and CO₂ above the basin.

  • Gas Dome 300 — black pyramid-shaped PVC hood floating on a basin of a wastewater treatment plant for nitrous oxide and methane monitoring
  • Gas Dome 300 — close-up of the floating hood with tube guide and rope mounting at the basin edge
  • Aerial view of a wastewater treatment plant with Gas Dome 300 deployed for continuous greenhouse gas emission monitoring

Illustration for reference only. The tube must be guided vertically upward.

How it works

From basin to gas analyzer

Rising greenhouse gases (N₂O, CH₄, CO₂) passively collect under the pyramid-shaped PVC hood. The resulting overpressure drives the collected gas through the vertically guided tube to the connected Fresenius gas analyzer — the actual measurement is performed in the gas analyzer.

Hood specifications

Construction in eight facts

Material
PVC
Shape
pyramid shape
Color
black
Buoyancy
floating
Weight
very lightweight compared to alternatives
Mounting
rope mounting on basin edge
Tube guide
guide construction for straight tube
Installation
easy to deploy

Measurement methods

What happens inside the gas analyzer

Non-dispersive infrared spectroscopy

The standard for online measurement of CO₂, CH₄, CO and many hydrocarbons. An IR source shines through the cell; the target gas absorbs a characteristic wavelength — the residual intensity yields the concentration directly.

Typical gases
CO₂ · CH₄ · CO · HC

Non-dispersive UV absorption

For gases that absorb in the UV range: NO, NO₂, SO₂. The method is selective and stable — robust against cross-sensitivity from other components in the off-gas.

Typical gases
NO · NO₂ · SO₂

O₂ measurement with no moving parts

Oxygen is paramagnetic and is deflected in a magnetic field. Our cell has no moving parts, so it is vibration-insensitive and long-term stable — ideal for wastewater plants and industrial environments.

Typical gases
O₂

Trace components and H₂S

Compact sensor technology for H₂S, H₂ and other components. The method combines low cross-sensitivity with a low detection limit — a typical add-on alongside NDIR cells.

Typical gases
H₂S · H₂ · O₂

Diode laser spectroscopy for CH₄

High-precision methane measurement via absorption of a single narrow-band laser line. Highly selective, highly stable — used by us exclusively for CH₄, e.g. in the Biomethane TDLAS.

Typical gases
CH₄

Advice

Tory — your Gas Dome 300 advisor

Which basins on your plant are candidates for the hood? Which gas analyzer matches your measurement goals? Tory guides you to the right configuration in just a few steps — or straight to a meeting with our team.

  • Suitable hood placement on your plant
  • Choice of gas analyzer (GA series, BioBasic, Biomethane TDLAS)
  • Direct path to a quote request

Cloud Connect Kit

Data from the hood to your dashboard

The Cloud Connect Kit (CCK) connects the attached gas analyzer to our dashboard platform. Spot measurements become continuous monitoring — trends, thresholds, reports for your GHG inventory.

  1. 01

    Hood captures emissions

    CH₄, N₂O, CO₂ — passively collected above the basin.

  2. 02

    Gas analyzer measures and streams

    Values are picked up by the Fresenius gas analyzer and streamed to the cloud via the CCK.

  3. 03

    Evaluate in the dashboard

    Trends, threshold alerts, reports — ready for audits and reporting.

Frequently asked

Gas Dome 300 FAQ

Which greenhouse gases does the Gas Dome 300 capture at a wastewater treatment plant?
The floating PVC hood passively collects all gases rising from the basin — for the GHG inventory the relevant ones are nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂). Under IPCC AR6, N₂O has a 100-year global warming potential (GWP) of 273 × CO₂ and methane of 27.9 × CO₂ — a direct off-gas measurement replaces the coarse IPCC Tier-1 default emission factors.
Which gas analyzers is the Gas Dome 300 compatible with?
All extractive Fresenius gas analyzers: GA150, GA210, GA220 (including GA220 Biomethane), BioBasic and Biomethane TDLAS. Modularity is a key difference from hardwired solutions — pick the gas analyzer that matches your measurement goals and swap it later without touching the hood installation.
On which basins of a wastewater plant can the Gas Dome 300 be deployed?
On any open basin — aeration, clarification, primary settling, sludge storage, digester inlet, filtrate. Thanks to its low weight and rope mounting at the basin edge, the hood can be repositioned quickly — ideal for comparative campaigns across multiple basins.
How accurate is the nitrous oxide measurement with the Gas Dome 300?
Accuracy comes from the connected gas analyzer, not the hood. The hood ensures a representative off-gas sample without cross-contamination from ambient air. With a Fresenius NDIR/NDUV unit you typically reach ppm resolution — enough to underpin IPCC Tier-3 reporting.
Which regulatory requirements does direct N₂O measurement with the Gas Dome 300 support?
Denmark introduced a binding N₂O limit value in its 2025 climate plan for wastewater plants ≥ 30,000 PE — the goal is to cut N₂O emissions from biological wastewater treatment by 50 %. Comparable rules are in preparation at EU level via the CSRD. Continuous off-gas measurement via a floating hood is recognised as defensible IPCC Tier-3 data — significantly more precise than the default emission factors of the Tier-1 method.
How much effort does it take to install the Gas Dome 300?
Very little. The hood is lightweight (PVC), fastened with two ropes to the basin edge and needs no structural change to the basin. The tube guide mounts on a simple frame. An experienced service crew typically completes the first installation in under a day per basin.
How is the Gas Dome 300 fastened — and is it winter-proof?
The hood floats freely and is tethered with two ropes to fixed points on the basin edge. PVC is UV- and frost-resistant — the construction stays in the basin year-round. If ice forms on the water surface, we recommend a short inspection before resuming measurement.
Can multiple basins be monitored simultaneously with the Gas Dome 300?
Yes. Each basin gets its own hood plus tube. The tubes can either route to a central multiplex cabinet, or each basin gets its own Fresenius gas analyzer. Combined with the Cloud Connect Kit (CCK), this creates a continuous, per-basin GHG inventory.
What is the advantage over fixed off-gas hoods, multiplex systems or grab samples?
Fixed off-gas hoods are expensive and structurally invasive. Multiplex systems (a central measurement station rotating between several hoods) only provide a per-hood snapshot at the minute scale — but N₂O emissions vary strongly with time of day, aeration regime and loading. Grab samples (bags, canisters) are not representative. The Gas Dome 300 delivers a continuous, per-basin off-gas sample — fed directly into a dedicated Fresenius gas analyzer — while staying easy to deploy.
Can the measurement data be exported into a GHG inventory or reporting system?
Yes — with or without the cloud, your choice. Directly at the Fresenius gas analyzer you get the classic industrial interfaces: analogue 4–20 mA outputs, RS232 / RS485, Profibus DP, Profinet, EtherNet/IP and Modbus TCP — so the values can be fed straight into your SCADA, PLC or DCS without any internet connection. For cloud-based monitoring, trends and reporting, the Cloud Connect Kit (CCK) additionally streams the values into our dashboard — from there you can generate reports for IPCC-compliant GHG reporting, ESG reports or CSRD annexes.

Request a consultation

Put your GHG inventory on defensible measurement data

We discuss with you for free which Fresenius gas analyzer matches your measurement goals — and how to combine the hood, gas analyzer and Cloud Connect Kit into a continuous, audit-ready data foundation for your GHG inventory. Outcome: a concrete proposal for a measurement campaign or a permanent installation.

Request a free consultation

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GAS ANALYZERS · MADE IN GERMANY · SINCE 1848