Summary form only given. An experiment has been conducted in a rectangular waveguide to study the effectiveness of plasma torches on microwave absorption. Three torch modules are mounted on the bottom wall of a rectangular X-band waveguide (1 in./spl times/2 in.), so that the plasma produced by the torch crosses the path of propagation of the microwave source (HP8620C) operating in the CW mode which is used to provide input power (-10 dBm) at the frequency of 10 GHz. The signals received at the other end of the waveguide are monitored with an HP856913 spectrum analyzer sweeping in real time. The attenuation of the microwaves for the three cases of one to three torches lit up is reported. In the process of carrying out the experiment, a new technique is also developed to measure the density and temperature of the plasma torches.