No direct gas sampling at high temperature fumaroles has yet been done at Santiaguito. In the late 1960's high temperature fumaroles were accessible in the region of the Caliente Vent and gas condensates were collected (Stoiber and Rose, 1970).

From early 1964 to April 1967, strong fumarolic activity was observed in the Caliente Crater. This fumarolic acitivity has evidently persisted for a number of years before 1964, at least since Meyer-Abich (1956) described its location in September 1954. The major fumaroles in this crater were concentrated in the lowest part of the depression, along a structural trend directed NE. These fumaroles produced a large amount of gas, at least 90% of the total fumarolic emission at Santiaguito, and had surface temperatures as high as 843°. As the high temperatures might suggest, red hot rock was occasionally visible deep inside the fumaroles. Chemical data concerning the condensates collected at fumaroles in the crater are summarized in the table below.

TABLE: Summary of Miscellaneous Observations at Fumaroles of Santiaguito. Cl and F by specific ion electrode. B by colorimetric method using carmine.
(Stoiber and Rose, 1969)

Gas samples collected at Sapper fumarole, Santiaguito, Guatemala, on December 5, 1969, were analyzed by gas chromatography-mass spectrometry. A number of compounds were found, including saturated and unsaturated hydrocarbons, aldehydes, ketones, alcohols, aromatics, halogenated hydrocarbons, and inorganic sulfur compounds. The compounds are probably produced by heating of fossil soil or sedimentary layers by the magma.(Stoiber et al., 1971)