# The level of CO gas in air that causes immediate death is

$\begin{array}{1 1}(a)\;10ppm\\(b)\;100ppm\\(c)\;500ppm\\(d)\;1000ppm\end{array}$

Toolbox:
• Carbon monoxide is toxic to all aerobic forms of life. It is easily absorbed through the lungs. Inhaling even relatively small amounts of the gas can lead to hypoxic injury, neurological damage, and even death.
1000ppm
Hence (d) is the correct answer.
edited Apr 2, 2014