Intercepted fog is commonly of a good quality, but may be affected by air pollution, dirt on roofs or rust on metal sheets. If measures are taken to prevent the first polluted flush entering storage tanks, water can be fit for drinking and other domestic use with little or no treatment.
===Suitable conditions ===
Fog collection is most suitable for locations with frequent fog periods. Upland areas where fog is produced by the advection of clouds over the terrain or where clouds are forced to rise over mountains are most suitable, in areas of prevailing winds between 3 - 12 m/s and with no obstructions to wind flow. Fog formed on the ocean surface, or nocturnal radiation fogs in low-lying areas normally lack sufficient liquid water content or sufficient wind speeds for substantial water collection. Examine meteorological records and consult local people about their observations.
===Resilience to changes in the environment===
Changes in sea surface or atmospheric temperatures can change the height of cloud bases or influence the extent of the cloud decks. Therefore be sure to site the collection nets in the middle of the most dense region of fog. If climate change causes the cloud patterns to move, the nets will need to be moved to maximise the area of greatest fog density. Coastal and upland forests in temperate and tropical regions, where fog is greatest, will be most affected.
When fog collection is used for irrigation to increase forested areas or vegetation coverage, it can help to counteract the desertification process.
===Construction, operation & maintenance===
[[Image:Dropnet.JPG|thumb|right|200px|New design of fog nets called the [http://www.designboom.com/weblog/cat/8/view/9269/imke-hoehler-dropnet.html Dropnet] by German designer Imke Hoehler.]]
Once a polypropylene net is obtained, use it correctly in a double layer. This is normally either polypropylene or polyethylene, u/v protected, with 35% shade coefficient, Raschel mesh weave, and a 1mm fibre size. Efficiency increases with smaller mesh sizes and fibre width.
A polypropylene mesh has a lifetime of about ten years. In Nepal, operation and maintenance is difficult due to the unavailability of spare parts (mainly polypropylene mesh). Hence keeping stock of mesh and other spare parts is highly recommended. In high winds, nets would normally be taken down as part of normal operation and maintenance. Otherwise where fog collectors are remotely located, different designs are being researched which may provide increased robustness.
===Costs===
The costs vary depending on the size of the fog catchers, quality of and access to the materials, labour, and location of the site. Small fog collectors cost between US$75 and US$200 each to build. Large 40-m² fog collectors cost between US$1,000 and US$1,500 and can last for up to ten years. A village project producing about 2,000 litres of water per day will cost about US$15,000 (FogQuest, 2011). Multiple-unit systems have the advantage of a lower cost per unit of water produced, and the number of panels in use can be changed as climatic conditions and demand for water vary (UNEP, 1997). Community participation will help to reduce the labour cost of building the fog harvesting system.
** Cost per m<sup>2</sup> (Nepal, including reservoir and tap): US$60
===Field experiences===
According to the International Development Research Centre (1995), in addition to Chile, Peru, and Ecuador, the areas with the most potential to benefit include the Atlantic coast of southern Africa (Angola, Namibia), South Africa, Cape Verde, China, Eastern Yemen, Oman, Mexico, Kenya, and Sri Lanka.
* [http://balwois.com/balwois/administration/full_paper/ffp-587.pdf FOG AND DEW COLLECTION PROJECTS IN CROATIA.]
===Manuals, videos, and links===
{{#ev:youtube|_Xn7YTzPydE|200|right|Fog Water project in Eritrea.}}
* [http://www.fogquest.org FogQuest]
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===Acknowledgments===
* CARE Nederland, Desk Study: [[Resilient WASH systems in drought-prone areas]]. October 2010.
* [http://www.washdoc.info/docsearch/title/169828 Smart Water Harvesting Solutions: Examples of innovative, low cost technologies for rain, fog, and runoff water and groundwater.] (or [http://www.arcworld.org/downloads/smart%20water%20harvesting.pdf alternative link]) Netherlands Water Partnership, Aqua for All, Agromisa, et al. 2007.
* Schemenauer, Robert and Cereceda, Pilar. [http://www.tiempocyberclimate.org/portal/archive/issue26/t26art3.htm Tiempo: Fog Collection]
* [http://tech-action.org/Guidebooks/TNA_Guidebook_AdaptationAgriculture.pdf Technologies for Climate Change Adaptation: Agricultural Sector.] UNEP. August 2011.
