Editing Ammonia (section)

=== Gaseous ammonia ===
[[Sulfur sticks]] are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with [[quicklime]], when the characteristic smell of ammonia will be at once apparent.{{sfn|Chisholm|1911|p=863}} Ammonia is an irritant and irritation increases with concentration; the [[permissible exposure limit]] is 25&nbsp;[[Parts-per notation|ppm]], and lethal above 500&nbsp;ppm by volume.<ref>(OSHA) Source: Sax, N. Irving (1984) ''Dangerous Properties of Industrial Materials''. 6th Ed. Van Nostrand Reinhold. {{ISBN|0-442-28304-0}}.</ref> Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume.<ref name="Hurtado-2014">{{cite journal|last1=Hurtado|first1=J. L. Martinez|last2=Lowe|first2=C. R.|title=Ammonia-Sensitive Photonic Structures Fabricated in Nafion Membranes by Laser Ablation|journal=ACS Applied Materials & Interfaces|volume=6|issue=11|year=2014|pages=8903–8908|issn=1944-8244|doi=10.1021/am5016588|pmid=24803236}}</ref>

In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is [[ammonium chloride]] vapor) arises from the reaction between ammonia and HCl(g).<ref>{{Cite book |title=Holleman-Wiberg inorganic chemistry |date=2001 |publisher=Academic |isbn=978-0-12-352651-9 |editor-last=Holleman |editor-first=A. F. |location=San Diego, Calif. London |editor-last2=Wiberg |editor-first2=Egon |editor-last3=Wiberg |editor-first3=Nils |editor-last4=Eagleson |editor-first4=Mary |editor-last5=Brewer |editor-first5=William |editor-last6=Aylett |editor-first6=Bernhard J.}}</ref>