They soon found that duct tape leaked air so badly much of the cooling and heating was wasted--and that the tape frequently shrunk, dried up or separated.

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There are big bucks to be made in surgical and medical fabrics-gross profits for surgical packs, gowns, caps, masks, sponges, bandages and tape run 25% to 30%-and in allergen- and pollution-trapping filters for heating and air-conditioning (50% to 60%), both made by 3M.

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