Radon gas is another indoor pollutant receiving a great deal of attention. It is a colorless, odorless gas found in high concentrations in the soil in scattered areas throughout North America. It is a natural by-product of the decay of uranium and thorium, radioactive elements that occur naturally in the earth. When radon gas is released into the atmosphere, it dissipates harmlessly but becomes a hazard when it seeps into a closed structure such as a home. There are no safe levels of radon exposure, but EPA has set the level of concern at .4 picocuries per liter of air.
Carbon monoxide is another problem in many homes.
It is produced when petroleum products and wood are burned. Improperly vented gas appliances, wood-burning stoves, kerosene heaters, and tobacco smoke raise carbon monoxide levels indoors. Carbon monoxide also can enter your house when a vehicle is idling in an attached garage or near the house. At moderate levels, carbon monoxide can cause headaches and irregular heart beats. At higher levels, it can cause loss of consciousness and death.