Cellulosic insulation is often implicated in fires, and the raw material from which this insulation is usually manufactured is newsprint. The newsprint is produced by mechanical pulping of wood and subsequent bleaching of the pulp. Accordingly, we find that newsprint contains hemicellnloses and lignin as well as cellulose, and its pyrolysis and char combustion properties have been shown to resemble wood more closely than cellulose. The oxygen chemisorption activity of newsprint chars is considerably greater than for comparable cellulose chars and is at a maximum for chars prepared at 500"C. The lowest ignition temperature in oxygen occurred with chars prepared at 375"C and is probably associated with a maximum content of reactive aliphatic components in the char. The influence of black and colored inks on formation and reactivity of newsprint chars is significant. Black ink causes little change in the form of the weight loss curve when newsprint is heated in air, but suppresses subsequent ignition of the char. Colored inks increase the rate of oxidative pyrolysis weight loss (in air) and lower the subsequent ignition temperature of the char. The latter effects are shown to be associated with metal ions introduced during the color printing process. In all cases, the removal of metal ions by mild acid washing increases the temperatures required for ignition of chars.