Caravan 208B
Flight Crew Air Transport Pilot (ATP)
Physiological - Other
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury
General Physical Injury / Incapacitation
Aircraft; Human Factors
[While] enroute [I] activated the TKS [weeping fluid anti-ice] System for [its required weekly] check. All fresh air vents closed and bleed air off. Had to activate backup mode to see any flow of TKS fluid. Ran system for about 20 minutes. Experienced my usual symptoms even though all vents were closed. Those symptoms are: mild headache; nausea and sense of lightheadedness. The nausea and lightheadedness increased after landing and was accompanied by a general sense of fatigue. The lightheadedness precluded driving home for 50 minutes. Mild nausea continued for about 30 minutes. Headache and fatigue continued for about 2 hours. A sticky film covered the yoke; my hands and the uncovered portion of my arms. My only suggestion is to don [the crew] Oxygen Mask prior to activating the TKS system and continue wearing it until engine shutdown.
A C-208 Captain reported multiple physiological impairments following performing a required inflight check of the aircraft's TKS surface anti-icing system.