The answer to this depends on how you apply and which product you are using…
Host sponges dry carpet cleaner
If you are applying by hand when cleaning a very dirty carpet we recommend that you only apply enough to cover a 3m x 3m (9 square meters) area before brushing. If you apply to a larger area, it is possible that some of the cleaning agents may evaporate and your results will be unsatisfactory. If you are carrying out maintenance cleaning or cleaning a light or medium soiled carpet then you can apply up to 20 square meters before brushing. If you are applying with the Host applicator, you can apply to larger areas before you start brushing. The Host applicator applies the Host in small piles which hold the moisture for a longer time period. Therefore, you can apply up to 40 square meters of carpet before brushing. You must still brush the area in sections of 40 square meters at a time before moving to the next; otherwise, the Host will dry out too quickly and have very little effect on the carpet.
Host SJ (Special Job)
If you are using Host SJ the use guidelines are different. Apply Host SJ to an area of only 3 square meters before you begin brushing. Brush this area and then vacuum immediately. It is important to clean smaller areas and vacuum immediately when cleaning with SJ. For best results, SJ must be vacuumed while it is still damp. You may use the Host applicator with Host SJ; apply to smaller areas with the applicator as well.