Multiwall carbon nanotubes (MWCNTs) were generated from recycled low-density polyethylene (LDPE). The polymer was pyrolyzed at 800 degrees C in inert atmospheres, and the gaseous pyrolyzates-light hydrocarbons and hydrogen-served as carbon donors for the MWCNTs, which were catalytically grown by chemical vapor deposition (CVD) at 800 degrees C. This investigation examined the influences of carrier gas type and flow rate on the synthesis of MWCNTs on stainless steel wire cloth substrates. The influences of the carrier gases (nitrogen, helium, argon, or carbon dioxide gases) and their flow rates (0.1, 1, and 2 L/min) were both found to have significance on both the yields and the characteristics of the produced MWCNTs. The obtained yields were the highest and the tubes were the longest in nitrogen, due to an apparent, yet unexpected, rate-boosting effect of this nominally inert gas. The MWCNTs' purity in the obtained yields appeared to be enhanced at the highest examined flow rate (2 L/min).