Human lungs are sensitive to strong chemical vapours and other volatile organic compounds (VOCs).
Always ensure there is plenty of fresh air flowing when using hazardous chemicals.
If cleaning with hazardous chemicals in close quarters where good ventilation is not available, such as in a lift or toilet cubicle, use an appropriate mask or breathing apparatus, or select a different, less hazardous chemical. Ensure SDS have been read.
Switch on ventilation fans if installed.
NEVER sniff chemicals in containers.