AC500 pilot reported deviating from assigned altitude and neglecting oxygen face mask requirements.

Attributes
ACN	1759077
Time
Date	202008
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	Marginal
Light	Dusk
Aircraft 1
Make Model Name	Aero Commander 500 Series
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Single Pilot Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Instrument
Experience	Flight Crew Last 90 Days 120 Flight Crew Total 3200 Flight Crew Type 250
Events
Anomaly	Deviation - Altitude Overshoot Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Flight Deck / Cabin / Aircraft Event Other / Unknown Inflight Event / Encounter Weather / Turbulence

Narrative:

While climbing to complete a fire mapping mission; I was cleared to 17;000 ft. MSL. I asked for a block altitude of 17;000 ft. - FL190 due to the presence of a smoke column that would likely cause me to deviate from my assigned altitude. As I got closer to the column; my altitude shot up to 17;500 ft. Before I received further clearance. At some point I was cleared to FL210. I became so task saturated managing piston engines during the climb; attempting to complete the mapping mission with two camera operators in the backseat; avoiding the smoke column and negotiating block altitudes with ATC that I failed to change my nose cannula to a full face mask above FL180. I started to have extreme difficulty processing information in a timely manner; as well as making decisions and communicating effectively. After asking for a lower altitude; 17;000 ft.; I was able to think clearly and manage tasks and communication appropriately.

Original NASA ASRS Text

Title: AC500 pilot reported deviating from assigned altitude and neglecting oxygen face mask requirements.

Narrative: While climbing to complete a fire mapping mission; I was cleared to 17;000 ft. MSL. I asked for a block altitude of 17;000 ft. - FL190 due to the presence of a smoke column that would likely cause me to deviate from my assigned altitude. As I got closer to the column; my altitude shot up to 17;500 ft. before I received further clearance. At some point I was cleared to FL210. I became so task saturated managing piston engines during the climb; attempting to complete the mapping mission with two camera operators in the backseat; avoiding the smoke column and negotiating block altitudes with ATC that I failed to change my nose cannula to a full face mask above FL180. I started to have extreme difficulty processing information in a timely manner; as well as making decisions and communicating effectively. After asking for a lower altitude; 17;000 ft.; I was able to think clearly and manage tasks and communication appropriately.

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.