Technical Bulletin # 2017-1 WARDFlex MAX Fire Rated Construction WARDFlex MAX Corrugated Stainless Steel Tubing now meets the ASTM E84 flame spread and smoke density criteria of 25/50 or less. This allows installation in a plenum without the need to remove the coating from the CSST. In addition to these instructions all local building codes need to be followed when installing WARDFlex MAX in a plenum. Most building construction codes require materials located in a plenum to have a flame spread/smoke density index of 25/50 or lower. Local codes may differ from this criteria and should be reviewed to determine… Read More