In the short-channel structures developed, the vol. mass transfer coeffs. were 2-10 times as high as those for a 50 channels cpsi monolith. Triangular and sinusoidal channels were best. The vol. mass-transfer coeffs. for gauzes were 8-85 times higher that for a 200-cpsi monolith. Pressure drop for the structures was much higher than for monoliths, and the lowest was for triangles and sinusoids. Gauze structures enabled reactor length to be reduced to 1/20, but pressure drop rose 10 times as compared with a 200-cpsi monolith. The best triangular and sinusoidal short-channel structures enabled the reactor to be shortened to 1/5(th) and pressure drop to be reduced by 50% as compared with the 50-cpsi monolith. The mass-transfer and pressure drop data were exptl.; structure characteristics were calcd. But none was checked in VOC combustion runs for which they were,A intended.