Carbon monoxide is colorless, odorless, and kills without warning. It is produced by every internal combustion engine and any device burning fossil fuel — generators, propane heaters, concrete saws, and forklifts. On NYC construction sites, CO poisoning spikes every winter when combustion equipment is brought indoors for warmth or convenience. Multiple workers have died in NYC building construction from CO poisoning in the last decade.

• CO is lighter than air but mixes rapidly with room air — it concentrates in any area where combustion equipment operates without adequate ventilation
• At 70 ppm: headache, dizziness, and fatigue begin. Workers often attribute these symptoms to dehydration or tiredness and stay on the job
• At 200 ppm: severe symptoms develop within 2–3 hours. OSHA PEL: 50 ppm (8-hour TWA)
• At 1,200 ppm (IDLH): unconsciousness within minutes; death follows quickly
• Because early symptoms mimic other conditions, workers frequently do not recognize CO poisoning until it is severe

• Never operate any gasoline, diesel, or propane combustion equipment inside a building — period. This includes generators, concrete saws, air compressors, and forklifts
• Electric tools and equipment inside buildings only — if the task requires an engine-powered tool, the exhaust must vent to the exterior
• CO detectors: required in all enclosed work areas where combustion equipment might operate nearby. Test monthly; replace per manufacturer schedule
• Propane heaters (salamanders): require 4 ACH (air changes per hour) minimum ventilation — document ventilation adequacy in the CSFSM daily log