TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The blowing agent comprises hydrofluorocarbon (1-99, preferably 70-90 wt.%); acid (1-99, preferably 10-30 wt.%); and water (0-98, preferably 0-5 wt.%).Preferred Components: The hydrofluorocarbon is pentafluoropropane isomer (HFC-245), difluoromethane (HFC-32), difluoroethane isomers (HFC-152), trifluoroethane (HFC-143), tetrafluoroethane isomer (HFC-134), pentafluoroethane isomer (HFC-125), hexafluoropropane isomer (HFC-236), heptafluoropropane isomer (HFC-227), pentafluorobutane isomer (HFC-365), fluoroethane isomer (HFC-161), difluoropropane isomer (HFC-272), trifluoropropane isomer (HFC-263), tetrafluoropropane isomer (HFC-254), fluoropropane isomer (HFC-281), hexafluorobutane isomer (HFC-356), decafluoropentane isomer (HFC-43-10mee), chlorodifluoroethane isomer (HCFC-22), dichlorofluoroethane isomer (HCFC-141 b), dichlorotrifluoroethane isomer (HCFC-123), chlorotetrafluoroethane isomer (HCFC-124), perfluoroethane, perfluoropropane, perfluorobutane, perfluorocyclobutane, dichloropropane, and/or difluoropropane, or preferably 1,1,1,3,3-pentafluoropropane (HFC-245fa).The acid is monofunctional carboxylic acid, difunctional carboxylic acid, and/or hydroxy acid. The monofunctional carboxylic acid is 1-6C monofunctional carboxylic acid, preferably formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, methylethylacetic acid, trimethylacetic acid (pivalic acid), n-caproic acid, methyl-n-propylacetic acid, 3-methylpentanoic acid, isobutylacetic acid, dimethylethylacetic acid, methylisopropylacetic acid, and/or t-butylacetic acid. The difunctional carboxylic acid is 1-6C difunctional carboxylic acid, preferably oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, methylsuccinic acid, dimethylmalonic acid, beta-methylglutaric acid, ethylsuccinic acid, alpha,alpha-dimethylsuccinic acid, isopropylmalonic acid, fumaric acid, and/or maleic acid.The hydroxy acid is 1-6C hydroxy acid, preferably hydroxyformic acid, hydroxyacetic acid, beta-hydroxypropionic acid, lactic acid (alpha-hydroxypropionic acid), glycolic acid, glyceric acid, tartaric acid, malic acid, diglycolic acid, erythronic acid, alpha-hydroxybutyric acid, gamma-hydroxybutyric acid, dl-threo-2,3-dihydroxybutyric acid, dl-erythro-2,3-dihydroxybutyric acid, alpha-hydroxyvaleric acid, alpha-hydroxy-alpha-methylbutyric acid, beta-hydroxyisovaleric acid, 2,3-dihydroxypentanoic acid, alpha-hydroxycaproic acid, epsilon-hydroxycaproic acid, alpha-hydroxy-alpha-methylvaleric acid, beta,beta,beta-trimethyllactic acid, 2,3-dihydroxyhexanoic acid, citric acid, and/or gluconic acid. The acid is formic acid. EXAMPLE - Foam was prepared from polyether polyol 1 (67.8 pbw), polyester polyol (20 pbw), amine polyol (7.6 pbw), polyether polyol (4.6 pbw), surfactant (1 pbw), catalyst (1.8 pbw), flame retardant (2.8 pbw), water (0.5 pbw), and formic acid (35.5 pbw).