Wood: A product of hard secondary xylem composed of CELLULOSE, hemicellulose, and LIGNANS, that is under the bark of trees and shrubs. It is used in construction and as a source of CHARCOAL and many other products.Pinus: A plant genus in the family PINACEAE, order Pinales, class Pinopsida, division Coniferophyta. They are evergreen trees mainly in temperate climates.Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Lignin: The most abundant natural aromatic organic polymer found in all vascular plants. Lignin together with cellulose and hemicellulose are the major cell wall components of the fibers of all wood and grass species. Lignin is composed of coniferyl, p-coumaryl, and sinapyl alcohols in varying ratios in different plant species. (From Merck Index, 11th ed)Dust: Earth or other matter in fine, dry particles. (Random House Unabridged Dictionary, 2d ed)SmokePlant Stems: Parts of plants that usually grow vertically upwards towards the light and support the leaves, buds, and reproductive structures. (From Concise Dictionary of Biology, 1990)Xylem: Plant tissue that carries water up the root and stem. Xylem cell walls derive most of their strength from LIGNIN. The vessels are similar to PHLOEM sieve tubes but lack companion cells and do not have perforated sides and pores.Air Pollution, Indoor: The contamination of indoor air.