Formaldehyde and nitrogen dioxide have been implicated as a cause of "sick house syndromes in which chemical allergens released in homes cause asthma and other respiratory ailments. Health organizations including WHO and the United States' ASHREhave established standards for safe indoor levels of these allergens. The Japanese government is investigating adoption of similar standards. Another important approach to this problem is the development of filter compounds capable of absorbing thesesubstances. MEW has tested numerous compounds for effectiveness in combination with activated charcoal and discovered absorbents for each of the allergens that are capable of one-pass filtering. The filter compounds outperform activated charcoal alone and have demonstrated a one-year service life under practical conditions.
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