Carbon Monoxide (CO) forms a very stable compound with Hemoglobin (Hgb) Its affinity for Hgb is several times that of oxygen (O2) with which it forms an unstable compound. The instability of Hgb-O2 is exquisitely programmed to let it give off the O2 to the tissues as the blood courses through them thus meeting their need for O2. If the blood contains a high percentage of Hgb-CO that has displaced the Hgb-O2, the amount of O2 is insufficient to meet the O2 needs of the tissues, resulting in death or, in the case of less severe exposures, tissue damage. If I remember correctly, smokers have an average of 5 or 6% of their Hgb in the form of Hgb-CO. Bob Howard Bob Howard, occasionally knowm formally as: Robert B. Howard 1312 Wisconsin St., Apt. 104 Hudson, WI 5401 CG for Lorraine 76/11 e-mail <[log in to unmask]> Voice phone: (715) 386-3596 FAX: (715) 386-8589 Manual reception, requires phone call.