Space-Ray (booth 1323) has expanded its line of unitized low-intensity gas-fired infrared LTU series U-tube heaters. Available in both natural and propane gas, the Space-Ray LTU series tube heaters are well-suited for high air change environments and higher mounting heights of 12 feet or more. The line has been expanded to 21 different models, with heating capacities from 40,000 to 250,000 Btu/hr. Space-Ray.