1. twice as bad
   four times as bad
2. ten times as bad

Enclosed space without proper ventilation can lead to a buildup of hazardous pollutants.

1. formaldehyde
   chlorine
2. nitrogen

This home kit tests for all sorts of air pollutants. Others include carbon monoxide and dioxide, bacteria and various fungi.

1. half
   75 percent
2. 90 percent

Compound this with the fact that indoor air pollution can come from various normal household sources, and checking indoor air quality becomes essential.

1. 35 percent
   65 percent
2. 75 percent

With so much time spent at home, it would make sense to ensure that the air there is safe to breathe and clean.

1. coma
   heart disease
2. hair loss

The consequences of breathing in indoor air pollution can be quite serious. Lung cancer is another serious potential effect.

1. fiberglass
   pleated
2. electrostatic

While fiberglass filters are the most cost-efficient, electrostatic filters combine the physical strengths of a pleated filter with the ability to attract even more particles using an electric charge.

1. Minimum Efficiency Reporting Value
   Maximum Effectiveness Recorded Value
2. Micro-Electric Range Value

The American Lung Association recommends a minimum MERV rating of 10.

1. wire coatings
   insulation
2. carpets

Polychlorinated biphenyl, or PCB, still remains in a number of household sources, including sealants and wood floor finishes.

1. asbestos
   formaldehyde
2. fluorine

Asbestos was a very popular building material for many years, particularly for insulation purposes. Removing it can be a costly and complex job.

1. pressed wood
   glass
2. plastics

Pressed wood can be used for subflooring, inexpensive furniture or shelving. Some paints may also contain formaldehyde.

1. underneath the home
   the local air
2. the house's water supply

Radon is a radioactive gas that can enter a home from the bedrock beneath it.

1. pollen
   pesticides
2. tobacco smoke

Other biological contaminants include mold, animal dander, viruses and even cockroaches.

1. carbon monoxide
   nitrous oxide
2. chlorine

If you heat your home using a solid fuel such as wood or coal, you must ensure proper ventilation for the harmful gasses to escape.

1. 30 percent
   55 percent
2. 80 percent

Up to 12 different pesticides have been measured inside. Thus pesticides are among the serious air pollutants that affect indoor air quality.

1. significantly worse
   about the same
2. much better

Commercial jets employ high quality air filtration and ventilation systems. They may remove up to 63 percent of the contaminants.

1. high levels of formaldehyde
   exposed fiberglass
2. PCB contamination

Three years after they were given out, many of the trailers were replaced when the problems were finally recognized.

1. 24
   97
2. 200

In addition, it contains at least 43 known carcinogens. The American Lung Association reports that secondhand smoke causes the deaths of around 3,000 people due to lung cancer each year, and many more due to heart disease.

1. by preventing oxygen from flowing through your body
   by increasing the risk of cancer
2. by reducing the immune system's effectiveness

Such gases are associated with a host of symptoms, such as dizziness or fatigue. At high levels, inhalation can lead to unconsciousness or even death.

1. if you live in a very humid area
   when it is particularly warm outside
2. if you have a radon pollution problem

Letting moisture into your home can lead to the growth of mold, another air quality pollutant. Humidity in the house should be kept at 30 to 50 percent.

1. that most are ineffective
   that only the very expensive ones work, and they may not be worth the cost
2. that they can actually harm the indoor air quality by raising ozone levels

High ozone levels are bad for asthma and can lead to chest pain and poor breathing.