A process for the production of plastic foams, preferably rigid foams containing urethane groups or urethane and isocyanurate groups, by reactinga) an organic and/or modified organic polyisocyanate withb) at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms, and, if desired,c) a low-molecular-weight chain extender and/or cross-linking agent,in the presence ofd) a blowing agent,e) a catalyst and, if desired,f) assistants and/or additives,in which the blowing agent (d) used is at least one vinylfluoroalkane of the formula CH.sub.2 .dbd.CH--C.sub.n F.sub.2n+1 in which n is an integer from 1 to 6, (di), or a mixture of at least one such vinylfluoroalkane (di) and at least one further physical and/or chemical blowing agent (dii) which is different from (di), blowing agent-containing emulsions which contain at least one vinylfluoroalkane and at least one starting component (a), (b), (c) or (b) and (c) and said plastic foams containing at least one vinylfluoroalkane as insulating gas.