Formic acid indoors

Pitts, J. N., Jr., H. W. Biermann, E. C. Tuazon, M. Green, W. D. Long, and A. M. Winer, Time-Resolved Identification and Measurement of Indoor Air Pollutants by Spectroscopic Techniques Nitrous Acid, Methanol, Formaldehyde, and Formic Acid, J. Air Pollut. Control Assoc., 39, 1344-1347 (1989). 

Carboxylic acids The smallest carboxylic acid, formic acid, can be measured using infrared spectroscopy (Table 11.2), since it has characteristic absorption bands. As discussed earlier and seen in Fig. 11.33b, mass spectrometry with chemical ionization using SiF5 also revealed HCOOH in an indoor environment (Huey et al., 1998). However, since the sensitivity in these initial studies was about two orders of magnitude less than that for HN03, the detection limit may be about the same as that for FTIR and TDLS. Formic and acetic acids have been monitored continuously from aircraft (Chapman et al., 1995) and their surface flux determined by eddy correlation (Shaw et al., 1998) using atmospheric pressure ionization mass spectrometry. Detection limits are about 30 ppt. 

Since formaldehyde is a reducing agent, devices have been constructed to remove it by means of a redox reaction. Indoor air is circulated through an air purifier containing an oxidant such as Al203/KMn04, which converts formaldehyde to the less harmful and less volatile formic acid (HCOOH). Proper ventilation is the best way to remove formaldehyde. However, care should be taken not to remove the air from a room too quickly without replenishment, since a reduced pressure would cause the formaldehyde resins to decompose faster, resulting in the release of more formaldehyde. 

Nielsen G.D., Hansen L.R, Nex0 B.A., Poulsen O.M. (1998 a) Indoor Air Guideline Levels for Formic, Acetic, Propionic and Butyric Acids. Indoor Air Suppl. 5, 8-24. 

The use of ultrasounds to aid the extraction is another possibility. Phthalates (Abb et al. 2009) and perfluorinated alkanoic acid (PEA) (Kato et al. 2009) determinations have been reported. Ethyl acetate (phthalates) or formic acid with methanol (perfluoroalkyl chemicals) was added to the dust sample, and extraction was performed in an ultrasonic bath at room temperature for 10 min. In the case of phthalates an enrichment step was not carried out to avoid the risk of contamination. Pyrethroids and their metabolites can also been extracted from indoor dust samples by adding methylene chloride followed by sonication for 10 min (Starr et al. 2008). Another option is the combination of Soxhlet extraction with an ultrasonic treatment (Schecter et al. 2009). 

The urea - formaldehyde (UF) and melamine-formaldehyde systems represent similar hazards. Free formaldehyde, which can be present in trace amounts, may be liberated to the air when resins are processed or even slowly afterwards, which can irritate the mucous membranes. Formaldehyde is a metabolite occurring normally in the human body and is converted to formic acid by enzymic oxidation. Formaldehyde in the cured resin is believed to be due to the unreacted free formaldehyde left (there are also claims that it may be due to demethylolation reaction and/or cleavage of methylene-ether bridges as well). A model specification to set out the health hazards is presented for polymer mortar surfacings (out of epoxy, polyester and PU thermosets), intended for their use as indoor floor tappings [39]. 

Wood is usually used as a building material and not as a cladding of metallic materials however, sometime wood parts are used in contact with metallic materials, for storage and packaging, and furthermore, metallic components are used as joints for wood parts. Wood contains ceUnlose, hani-cellulose, lignin, and water in equilibrium with atmospheric humidity, and also complex substances such as acetylated polysaccharides. Some of these substances, by hydrolysis, generate acetic acid, and others release formic acid, propionic acid, and butyric acid, all volatile substances that can dramatically affect the behavior of the atmosphere, especially in indoor environments. On one hand, wood contains tannins, which combine with the metals and may give rise to protective corrosion... 

Chamber (Caltech Indoor Chamber Facility) experiments have also been carried out by Lee et al. to monitor the time evolution and yields of gas-phase VOCs produced by the ozonolysis of ten different terpenes [197] six monoterpenes (a-pinene, (3-pinene, 3-carene, terpinolene, a-terpinene and myrcene), two sesquiterpenes (a-humulene and p-caryophyllene) and two oxygenated terpenes (methyl chavicol and linalool). Several gas-phase oxidation products were identified including formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, nopinone and pinonaldehyde. 

Figure 15.12 summarizes the ratio of indoor-to-outdoor concentrations of HCHO and higher aldehydes as well as formic and acetic acids measured in some conventional homes. Concentrations of all of these compounds, except possibly propionaldehyde, are significantly higher indoors, suggesting that not only... 

FIGURE 15.12 Ratio of indoor-to-outdoor concentrations of formic and acetic acids and some carbonyl compounds in some homes unshaded, data from Reiss et al., 1995a, for summer data shaded, data from Zhang et al., 1994a. 

The relevant material components in indoor environments can be conveniently segregated into six categories. Corrosive gases include SO2 and NOx (primarily NO and NO2), as well as organic acids such as formic and acetic... 

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