Sure you're reading the correct supplement?
AW139 RFM, rev. 22, Sup. 12 CAT A, offshore helideck landing:
6. HEATER (if used) — Confirm SOV 1 & 2 switches selected to NORMAL - Select HTR switch to OFF, note ITT decrease and confirm HEATER ON advisory extinguished.
ECS ENVIRO (if used) — Confirm SOV 1 & 2 switches selected to NORMAL - Select ECS CONTROL switch to OFF and, if HEATER ON advisory illuminated, note ITT decrease and confirm HEATER ON advisory extinguished.
Hope this helps.