The technician performed the job as well as anyone. I was unhappy, however, with his attempt to sell me a high-cost, specialty carbon monoxide detector by scaring me into thinking my current detectors were somehow ineffective. He made a big show of checking the labels of my detectors and saying that he didn't think they were sensitive enough, when in fact all CO detectors are standardized. He of course knew this. While performing the evaluation he also stuck William Henderson stickers on my hot water heater and air conditioning unit, neither of which he serviced or checked. The tech also said we had restricted air to the furnace and that would reduce the life of the furnace because of possible overheating of the exchanger. He proposed installing a wider, deeper return air drop and turning boot--for about $2,400. I brought in a tech from a different company for a second opinion who said that there was no problem with the air flow.