The Food and Drug Administration has rated n-Butane and Isobutane as GRAS, or generally recognized as safe. https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol3/pdf/CFR-2012-title21-vol3-sec184-1165.pdf Food and Drug Administration, HHS § 184.1165 n-Butane and iso-butane. (a) n-Butane and iso-butane (empirical formula C4H10, CAS Reg. Nos. 106– 97–8 and 75–28–5, respectively) are colorless, flammable gases at normal temperatures and pressures. They are easily liquefied under pressure at room temperature and are stored and shipped in the liquid state. The butanes are obtained from natural gas by fractionation following absorption in oil, adsorption to surface-active agents, or refrigeration. * (b) The ingredients must be of a purity suitable for their intended use. * (c) In accordance with §184.1(b)(1), these ingredients are used in food with no limitations other than current good manufacturing practice. The affirmation of these ingredients as generally recognized as safe (GRAS) as direct human food ingredients is based upon the following current good manufacturing practice conditions of use: (1) The ingredients are used as propellants, aerating agents, and gases as defined in § 170.3(o)(25) of this chapter. (2) The ingredients are used in food at levels not to exceed current good manufacturing practice. (d) Prior sanctions for these ingredients different from the uses established in this section do not exist or have been waived. [48 FR 57270, Dec. 29, 1983, as amended at 73 FR 8607, Feb. 14, 2008; 76 FR 59249, Sept. 26, 2011]"