Without wanting to be pedantic:
Your % can never be the correct ones, see the concentration tabel below, maybe you mean the COHB value ? ( CO to Hemoglobin bound in %)
A 0,5 % of CO, in breathing air, will kill you in minutes
Yes, standard Pulsoxymeters will not do good diagnostics, therefor the 7 wavelength pulsoxymeter now available (mandatory in the fire truck )
35 ppm (0.0035%) Headache and dizziness within six to eight hours of constant exposure
100 ppm (0.01%) Slight headache in two to three hours
200 ppm (0.02%) Slight headache within two to three hours; loss of judgment
400 ppm (0.04%) Frontal headache within one to two hours
800 ppm (0.08%) Dizziness, nausea, and convulsions within 45 min; insensible within 2 hours
1,600 ppm (0.16%) Headache, increased heart rate, dizziness, and nausea within 20 min; death in less than 2 hours
3,200 ppm (0.32%) Headache, dizziness and nausea in five to ten minutes. Death within 30 minutes.
6,400 ppm (0.64%) Headache and dizziness in one to two minutes. Convulsions, respiratory arrest, and death in less than 20 minutes.
12,800 ppm (1.28%) Unconsciousness after 2–3 breaths. Death in less than three minutes.