An application device for applying a composite substance onto a site is provided that operably applies a composite substance formed of at least two reaction substances which react with one another. In one aspect, this improvement is achieved by conducting a pre-deposition spacer deposition process wherein a temperature of a bottom region of a furnace is higher than a temperature of in the top region and is maintained for a predetermined period. The upstream surface contour and the downstream surface contour of the vent inlet surface are substantially oblique to the local external flow direction.