Narrative:

Descending on a reposition flight to 11;000 ft we encountered ice and received two caution messages: wing anti-ice fail and stabilizer anti-ice fail; followed shortly by the warning message: anti-ice fail. We verified that the valves had opened and they had; so the first officer switched the anti-ice knob to all. I asked him to tell ATC that we needed to descend below the cloud layer; which was approximately 7;000 ft. The first officer declared an emergency and requested an immediate descent. At the same time he was making his call it dawned on me what the problem was: during the 10;000 ft flow [checklist] the bleeds were never switched over from the APU to the engines. I switched the APU bleed off and the engine bleeds on. The anti-ice worked properly and all messages were extinguished. I told the first officer to cancel the emergency and we remained at 11;000 ft. The entire event lasted no longer than approximately 10 seconds.I believe the first officer missed part of his 10;000 ft flow due to task saturation climbing out. When we received the aircraft the GPS had just been written-up by the prior crew. We were filed a non-standard route. During our climb we received a message on the FMS indicating that one of the IRS's was out of range. We were trying to determine whether the FMS was navigating on course correctly; and we were also tracking short range.being a relatively new captain this was a reminder that I need to remain vigilant and not assume; but verify that tasks have been completed. I should periodically look over the cockpit assuring that all systems are configured correctly.

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Original NASA ASRS Text

Title: During descent in icing conditions the crew of an EMB-145 received multiple anti-ice fail messages; declared an emergency; and requested an immediate descent to lower altitude. The Captain then realized the anti-ice bleed sources were incorrectly selected to the APU and were then properly selected to the engines; restoring normal operation.

Narrative: Descending on a reposition flight to 11;000 FT we encountered ice and received two caution messages: Wing anti-ice fail and Stabilizer anti-ice fail; followed shortly by the Warning message: Anti-ice fail. We verified that the valves had opened and they had; so the First Officer switched the anti-ice knob to ALL. I asked him to tell ATC that we needed to descend below the cloud layer; which was approximately 7;000 FT. The First Officer declared an emergency and requested an immediate descent. At the same time he was making his call it dawned on me what the problem was: during the 10;000 FT flow [checklist] the bleeds were never switched over from the APU to the engines. I switched the APU bleed off and the engine bleeds on. The anti-ice worked properly and all messages were extinguished. I told the First Officer to cancel the emergency and we remained at 11;000 FT. The entire event lasted no longer than approximately 10 seconds.I believe the First Officer missed part of his 10;000 FT flow due to task saturation climbing out. When we received the aircraft the GPS had just been written-up by the prior crew. We were filed a non-standard route. During our climb we received a message on the FMS indicating that one of the IRS's was out of range. We were trying to determine whether the FMS was navigating on course correctly; and we were also tracking short range.Being a relatively new Captain this was a reminder that I need to remain vigilant and not assume; but verify that tasks have been completed. I should periodically look over the cockpit assuring that all systems are configured correctly.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.