Floating hood for nitrous oxide and methane monitoring at wastewater treatment plants

Gas Dome 300

The floating hood captures nitrous oxide (N₂O), methane (CH₄) and CO₂ from a defined area of 1.00 m² directly above the aeration tank. It is the core of the Off-Gas System – with the Smart Control 300 (Smart) or the GA 320 (Expert).

Part of the Off-Gas System Compare Smart and Expert

4.8from 127 reviews

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

Floating hood for direct capture of nitrous oxide, methane and CO₂ from 1.00 m² of basin surface.

  • 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) collect under the hood over 1.00 m² of basin surface. Without a blower, driven by its own pressure, the off-gas flows through the hose, condensate trap, filter and flow measurement into the outdoor cabinet. There the analyzer – Smart Control 300 in the Smart system, GA 320 in the Expert system – measures and calculates the emission rate in mg/(m²·h).

Hood details (extract)

Construction in eight facts

Collection area
1.00 m² collection area (inside dimension)
Design
Pyramid on a PVC-U floating frame, dark PVC skin
Buoyancy
Closed-cell PE buoyancy insulation
Skirt
Skirt all round, 20–30 cm immersed, chain ballast
Connection
Tank feedthrough 1½″, 40 mm hose nozzle
Flow
Flow 0–20 m³/h, no blower
Positioning
Guy ropes or fixed bridge, boom for strain relief
Hose
Hose ID 40 mm, 25 m per measuring point, down to −20 °C

Extract, as of 06.10.2026. The Off-Gas System Smart and Expert brochures are binding.

Smart · Expert

With SC 300 or GA 320: 10 ppmV or 0.5 ppmV detection limit

The Gas Dome 300 comes with gas path and outdoor cabinet as the Off-Gas System. Which analyzer goes into the cabinet depends on how low your nitrous oxide values are.

Measurement methods

What happens inside the analyzer

Self-referencing, no zero or span gas

Both analyzers – Smart Control 300 and GA 320 – measure N₂O, CH₄ and CO₂ using the NDIR dual-pressure reference method. The zero point is corrected with every measurement, so the system needs neither zero gas nor span gas and no consumables. The GA 320 additionally compensates for humidity and cross-sensitivities.

Typical gases
N₂O · CH₄ · CO₂

Oxygen in the off-gas

Optionally, an electrochemical sensor measures the oxygen in the off-gas, range 0–30 vol.%.

Typical gases
O₂

Advice

Tory — your Gas Dome 300 advisor

Which basins on your plant are candidates for the hood? Is the Smart system enough, or do you need the detection limit of the Expert? 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 system: Smart (SC 300) or Expert (GA 320)
  • Direct path to a quote request

Frequently asked

Gas Dome 300 FAQ

Which gas analyzers does the Gas Dome 300 work with?
The Gas Dome 300 is supplied as part of the Off-Gas System, in two versions: Smart with the Smart Control 300 (N₂O detection limit 10 ppmV) and Expert with the GA 320 (N₂O detection limit 0.5 ppmV). Hood, gas path and outdoor cabinet are identical in both systems – the difference is the analyzer.
Which gases does the Gas Dome 300 capture at a wastewater plant?
The hood collects the off-gas rising from its area of the aeration tank. Measured are nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂), optionally oxygen via an electrochemical sensor (0–30 vol.%). Under IPCC AR6, N₂O has a 100-year global warming potential of 273 × CO₂.
What area does the Gas Dome 300 cover?
The collection area is 1.00 m² (inside dimension). The system does not measure the whole basin but a defined water surface – which is what makes the value comparable: concentration and flow give an emission rate in mg/(m²·h).
Does the Gas Dome 300 need a blower or pump?
No. The off-gas flows by its own pressure under the hood through the hose (ID 40 mm) to the outdoor cabinet. The permitted range is 0–20 m³/h. Below roughly 1 m³/h the system flags the reading as invalid.
How is the Gas Dome 300 held in place?
The pyramid sits on a square PVC-U floating frame with PE buoyancy insulation. A skirt all round is immersed 20–30 cm and weighted with chain ballast so that no ambient air gets under the hood. The position is secured with guy ropes or a fixed bridge; a boom takes the strain off the hose.
Can two basins or two points be measured at the same time?
Yes. Both systems work with one or two measuring points; each point has its own hood and 25 m of hose. The second point costs only a fraction, because the cabinet and analyzer are already in place.
Does it replace an official emission measurement?
No. The system delivers the emission rate of a defined area – not an official emission inventory and not a CEMS. For operational accounting, for example under the Urban Wastewater Treatment Directive, and to prove process optimisations, it provides measured instead of estimated values.
Where does the measurement data go?
It stays with you. The analyzer calculates the emission rate itself and outputs it via analogue and relay outputs and RS-232, optionally via Profibus DP, Modbus TCP, EtherNet/IP or Profinet. No cloud, no subscription, no ongoing licence fees.

Request a consultation

Put your GHG inventory on defensible measurement data

We discuss with you free of charge whether the Smart or Expert system fits your measurement goals, how many measuring points make sense and where hood and outdoor cabinet go on your plant. Outcome: a concrete proposal for a measurement campaign or a permanent installation.

Request a free consultation

Related

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Measuring What Matters

GAS ANALYZERS · MADE IN GERMANY · SINCE 1848