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Searching for the presence of circumstellar material is currently the onlydirect way to discriminate between the different types of possible progenitorsystems for Type Ia supernovae. We have therefore looked for narrow H-alpha ina high-resolution spectrum of the normal Type Ia supernova 1994D taken 10 daysbefore maximum and only 6.5 days after explosion. We derive an upper limit of2.0E-16 erg cm^{-2} s^{-1} for an unresolved emission line at the local H IIregion velocity. To estimate the limit this puts on wind density, we have madetime-dependent photoionization calculations. Assuming spherical symmetry wefind an upper limit of the mass loss rate which is roughly 1.5E-5 solar massesper year for a wind speed of 10 km s^{-1}. This limit can exclude only thehighest-mass-loss-rate symbiotic systems as progenitors. We discuss the effectof asymmetry and assess the relative merits of early optical, radio and X-raylimits in constraining mass loss from Type Ia progenitors. We find that X-rayobservations can probably provide the most useful limits on the progenitor massloss, while high-resolution optical spectroscopy offers our only chance ofactually identifying circumstellar hydrogen.Comment: 7 pages, LaTeX, 3 Postscript figures, mn.sty, psfig.tex; MNRAS, in  pres

Circumstellar H from SN 1994D and future Type Ia supernovae: an observational test of progenitor models