To put in in the nerdiest possible terms:
You have to make an HT-2 roll against each of Blindless, Coughing and Retching with each lasting 1+MoF minutes.
So healthy Spartans with HT12 have a 50% of each effect. So 12% will be totally useless for at least a minute, 76% will be at less than full potential and 12% will be unharmed.