I got blood work done after a carbon monoxide leak was discovered at work and came back with a 2.5 level. Is this a high level for a non-smoker?

Not high, but... Non-smokers in non-urban, non-industrial areas are probably under 1-2%. People living in urban, industrialized areas can be a little bit higher, so 2-3% sounds ok. Smokers can be at 4-8%, approximately. However, the half-life (how long it takes for a higher level to drop in half) is about 5 hours. The 2.5% could have been there always, or could have been a decrease from a level of 5%, 5 hours ago.