Ammonia is a highly reactive gas, an excess of which can lead to eutrophication and acidification of terrestrial and freshwater ecosystems, biodiversity loss and the formation of secondary particulate matter. It originates from both natural and anthropogenic sources, including agricultural related emissions such as manures, slurries and fertiliser application.

Ambient ammonia monitoring can be carried out with two CEH products: a low-cost passive sampler (ALPHA®) and the DELTA® active sampler system. The DELTA® system can also be used to actively sample a wider range of atmospheric species.

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The CEH ALPHA® and DELTA® systems

Alpha sampler  DELTA system  Shopping basket icon for ALPHA and DELTA order form

CEH ALPHA® for ammonia monitoring in air

The CEH ALPHA® (Adapted Low-cost Passive High Absorption) sampler is a system designed for the measurement of the concentration of ammonia (NH3) in air. It does not sample ammonium aerosol. It is useful as a complementary method for assessing spatial differences in source areas where NH3 concentrations may vary hugely. The method does not require electricity. 

Suitable range of ammonia concentrations:

Monthly monitoring = 0.02 - 100 ug NH3 m-3
Weekly monitoring = 0.05 - 400 ug NH3 m-3

The passive sampling system consists of three replicate ALPHA® samplers attached to the underside of a shelter at about 1.5m height above ground. The samplers operate on the principle of diffusion with an acid-coated filter which serves to capture the ammonia. More details of the scientific background and operation are supplied with the samplers. Replicate tubes are used in order to give more reliable results.

outline diagram showing an ALPHA sampler
Above: Outline diagram of a single ALPHA® sampler and components.

All of the plastic components of the ALPHA® samplers, including the PTFE membranes, can be cleaned and reused. The only component that is single use is the filter paper. 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:

ALPHA® components

ALPHA® sampler

Can be cleaned for re-use. Does not require electricity. Includes velcro patches to stick to shelter. Minimum order 20.

PTFE membrane

27mm PTFE membrane can be cleaned for re-use. One per ALPHA® sampler required. Minimum order 20.


24mm diameter cellulose filter circles (used once and replaced). Available in packs of 500 or 1000.


To house three samplers.

Sampler analysis

Exposed samples are stored at 4˚C until analysis. The chemical of interest captured on the filter paper or denuder tube is extracted, usually into deionised water, which is then analysed. At CEH we use AMFIA (AMmonia Flow Injection Analysis system) for ammonium analysis or Ion chromatography for other chemicals of interest. We use a set of standards and quality control samples to ensure accurate results.

Manual and help videos

How to prepare a CEH ALPHA® sampler

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.

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