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CEH air sampler systems for environmental monitoring

Alpha sampler

DELTA system

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DELTA® II system for measuring ammonia, ammonium, acid gases and aerosols

The CEH DELTA® (DEnuder for Long-Term Atmospheric sampling) system is a low-volume denuder air sampling method for long-term sampling of ammonia and ammonium in the atmosphere.

The system can also be extended to sample acid gases (NH3, HNO3, HCl, SO2) and aerosols (NH4+, NO3-, SO42-, Cl-, Na+, Ca2+, Mg2+).

monitoring enclosure of the low voltage CEH DELTA system

Above: Detail of components in the monitoring enclosure of the low voltage DELTA® system. An example installation of the low voltage DELTA® system powered by wind and solar in the field is shown on the right. 1: Durable plastic enclosure (ip 65) with clear lid/door. 2: Sample train holder. 3: Sample inlet (funnel as rain shield). 4: Plug-in mini-heater inside sample train holder to maintain temperature approx. 3 degrees Celsius above ambient. 5: G1.6 high sensitivity gas meter. 6: Rotameter. 7: Air pump (6v knf) and pcb (accepts voltage range of between 10  – 36v).

The DELTA® system is based on the concept of a coated single bore glass denuder. When a laminar air stream passes through the coated denuder, gases of interest react with and are captured by the coating. The coating is later extracted and analysed in a laboratory. Aerosols pass through the coated tube and can be collected by coated filters placed downstream of the denuder. The separation of aerosol from gaseous components is achieved due to the much more rapid diffusion of gaseous species to the tube wall compared with that of particles.

Low, stable air sampling rates of 0.2-0.4 / min-1 are achieved using small air pumps, with air volumes being measured by a high sensitivity dry gas meter. The low sampling rate means that short glass denuders can be used, which allows easy exchange of samples through the post. A simple enclosure is used, which can be mounted easily in the desired location (typically 1.5 above ground for short grass). The DELTA® system can be run from mains power or using a solar panel/wind turbine and battery set-up for remote locations.


You can select which components you require on our order form and we will supply a quote. Details of what is available can be found below:

DELTA denuder assembly A

DELTA® components list

Low voltage (10-36v) DELTA® system

Mounting brackets fitted at the back of the enclosure as standard. The size used (size B) will fit over poles with an OD of 1 11/32 inch (~34.1mm). Other sizes can be mounted on request but additional charges may apply if they are more expensive. Two sample train holders are supplied with each DELTA system. *Denuder assembly (sample train) NOT included: see below for purchase detail.

Sample train components

All of these components are re-usable and represent a one-off purchase:

A. Denuder assembly for NH3 and NH4+ sampling (illustrated right)
Consisting of two component denuders, glass inlet, caps, one-stage filter pack and connecting silicone tubes. Minimum order 5.

B. Denuder assembly for sampling of NH3, acid gases + aerosol anions and cations
Consisting of four component denuders, 2.8cm Teflon inlet, caps, 2-stage filter pack and connecting silicone tubes. Minimum order 5.

C. Denuder assembly for sampling of NH3, acid gases (selective for HNO3) + aerosol anions and cations
Consisting of four component denuders, 2.8cm Teflon inlet, caps, 3-stage filter pack and connecting silicone tubes. Minimum order 5.


25mm diameter cellulose filter circles (used once and replaced). 500 per pack.

Manual and help videos

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Related publications

Martin Nicholas A, Ferracci Valerio, Cassidy Nathan, Hook Josh, Battersby Ross M, di Meane Elena Amico, Tang Yuk S, Stephens Amy C M, Leeson Sarah R, Jones Matthew R, Braban Christine F, Gates Linda, Hangartner Marcus, Stoll Jean-Marc, Sacco Paolo, Pagani, Diego, Hoffnagle John A, Seitler, Eva (2019). Validation of ammonia diffusive and pumped samplers in a controlled atmosphere test facility using traceable Primary Standard Gas Mixtures. Atmospheric Environment, 199. 453-462. DOI: 10.1016/j.atmosenv.2018.11.038

Tang Y Sim, Braban Christine F, Dragosits Ulrike, Simmons Ivan, Leaver David, van Dijk Netty, Poskitt Janet, Thacker Sarah, Patel Manisha, Carter Heather, Pereira M Gloria, Keenan Patrick O, Lawlor Alan, Connolly Christopher, Vincent Keith, Heal Mathew R, Sutton Mark A (2018). Acid gases and aerosol measurements in the UK (1999–2015): regional distributions and trends. Atmospheric Chemistry and Physics, 18 (22). 16293-16324. DOI:10.5194/acp-18-16293-2018

Tang, Y S, Braban, C F, Dragosits, U, Dore, A J, Simmons, I, van Dijk, N, Poskitt, J, Pereira, M G, Keenan, P O, Conolly, C, Vincent, K, Smith, R I, Heal, M R and Sutton, M A (2018) Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK, Atmospheric Chemistry and Physics, 18, 705-733, DOI: 10.5194/acp-18-705-2018.

Puchalski M A, Sather M E , Walker J T, Lehnmann C M B, Gay D A, Mathew J, Robarge, W P. (2011). Passive ammonia monitoring in the United States: Comparing three different sampling devices. Journal of Environmental Monitoring, 13, 3156.

Sutton M A, Miners B, Tang Y S, Milford C, Wyers, G P, Duyzer, J H and Fowler, D. (2001a) Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia. J. Environ. Monit. 3, 446‑453.

Sutton M A, Tang Y S, Miners B and Fowler, D (2001b) A new diffusion denuder system for long-term, regional monitoring of atmospheric ammonia and ammonium. Water, Air and Soil Pollution. Focus, 1, Part 5/6, 145‑156.

Tang Y S, Cape J N & Sutton M A. (2001) Development and types of passive samplers for monitoring atmospheric NO2 and NH3 concentrations. In Proceedings of the International Symposium on Passive Sampling of Gaseous Pollutants in Ecological Research. TheScientificWorld, 1, 513-529.

Tang Y S, Simmons I, van Dijk N, Di Marco C, Nemitz E, Dämmgen U, Gilke K, Djuricic V, Vidic S, Gliha Z, Borovecki D, Mitosinkova M, Hanssen J E, Uggerud T H, Sanz M J, Sanz P, Chorda J V, Flechard C R, Fauvel Y, Ferm M, Perrino C & Sutton M A (2009) European scale application of atmospheric reactive nitrogen measurements in a low-cost approach to infer dry deposition fluxes. Agriculture, Ecosystems and Environment: NitroEurope Special issue. (133), 183-195.