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Measure pH of air


Q. How I can measure pH of Air?

Nisar Arain
Engineer - Ras Al Khaimah, RAK, UAE


A. Hi, Mr. Arain. I don't think "air" per se really has a pH because I don't think there are hydronium ions in dry air, and pH is the negative log of the hydronium ion concentration. If you are talking about the exhaust air from a wet process that creates droplets, the tiny liquid droplets can have a pH, but I think they would probably be the same pH as the wet process tank. Can you clarify your situation for us a bit, so we have some idea whether you are studying an industrial process in a plant, or acid rain, or humidified air in a building or whatever? Thanks.

Ted Mooney,
Teds signature
Ted Mooney, P.E. RET
Pine Beach, New Jersey


A. There has to be a change in the acidity of air when other gases such as ammonia are dissolved in it. Perhaps this is a way to determine the health risks of pollution!

Dr. Smith

David W. Smith, M.D.
- San Dimas, California

December 7, 2011

A. It is possible to test air pH. Museums need to keep an eye on the pH of their air.

See this paper:

Air Pollutants Trapped in a "pH Test Paper for Indoor Air/Henshoku Shiken-shi".
Accession number;99A0753344
Title;Air Pollutants Trapped in a "pH Test Paper for Indoor Air/Henshoku Shiken-shi".
Author; SANO CHIE (Tokyo Natl. Res. Inst. of Cult. Prop.)
Journal Title;Science for Conservation
Journal Code:Y0449A
Figure&Table&Reference;FIG.6, TBL.4, REF.4
Pub. Country;Japan
Abstract;Indoor air pollution has become an menacing problem in many museums, but the cost for analyzing the air pollutants is so expensive that all museums cannot afford it. To evaluate the acidity of indoor air in museums, a specific test by a "pH Test Paper for Indoor Air/Henshoku Shiken-shi" is used in Japan, which has been used over twenty years. A "pH Test Paper for Indoor Air" is made by dipping in a glycerin/ethanol mixed solution dissolving four chromatophore; chlorophenol red, bromothymol blue, phenol red, and bromcresol green. The making procedure was also given in this paper. The concentration of inorganic ions by ion chromatography and of carboxylic acids by liquid chromatography were done to know the concentration of air pollutants trapped in a test paper. Ammonium ion was observed in every sample and its amount changed as the color of the pH test paper showing the "alkalinity" of an indoor air of a museum. Formic acid and acetic acid were observed only in the newly built museum. Author suggests that the usage of a "pH Test Paper for Indoor Air" is still useful, and also shows the possibility to estimate the quantity level of indoor air pollutants when measuring the quantity of trapped pollutants in a test paper. (author abst.)

John Mayor
- Annapolis, Maryland, USA

Ed. note: Thanks for a great response, John.

June 24, 2013

Q. Hi My name is Rich,
I deal with an SN electroforming process, I would like to know if the acidity of the air could be measured? If the acidity can be measured, can the measurement be used to evaluate the ventilation in the room?

Rich Conarroe
- Glenside, Pennsylvania, USA

July 8, 2013

A. Acid may exist as a fume or a mist. Either one can be measured down to the ppm level. I can't give you a brand name due to editorial policy, but there are simple, manually operated air pumps and tubes that will collect and quantify the concentration of acid.

You should be aware that there is also an OSHA PEL for acid fumes and mist.

Lyle Kirman
consultant - Cleveland, Ohio
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