Do HCN and CO produce scarring in the tissues?
According to Dr. Alan Hall, “The issues of CO and HCN causing scarring in the tissues are erroneous. Chronic sequelae of acute CO poisoning can be post-CO encephalopathy which can present as a delayed onset of generalized encephalopathy (a dead neuron here, and a dead neuron there that may not be apparent on typical CT/MRI scans). It may also present as bilateral lesions in the basal ganglia. Patients who have survived severe, acute cyanide poisoning may present in either manner, although these are patients who have had severe hypoxia and have required prolonged ICU treatment with high-level O2 and mechanical ventilation. There are only a handful of these patients identified in the world’s literature. With the basal ganglia lesions, they can present with what looks like Parkinson’s disease (but from a different pathophysiological mechanism).”

How does HCN affect the thyroid?
Dr. Alan Hall addresses the question relative to HCN and the thyroid:

“There are basically two scenarios here. If the body has enough sulfane sulfur available for endogenous rhodanese cyanide detoxicification, this produces thiocyanate. Thiocyanate looks to the thyroid like iodine (due to the similarities in physical-chemical properties), so the thryoid takes it up and tries to make thyroid hormones out of it. Naturally, this doesn’t work and results in hypothyroidism, and the hormonal feedback loops when hypothyroidism is present, causing the thyroid gland to enlarge as it would in patients with dietary iodine deficiency.”

Can HCN stay in the body for up to “8 days”?
According to Dr. Alan Hall, “Even after ingestion, it’s about 30-60 minutes for the acute phase when cyanide levels decrease from potentially fatal/toxic to non-toxic and about 19 hours or so after that (when it doesn’t really matter in terms of health issues because the levels are non-toxic). The Paris fire smoke studies have generally found the same 30-60 minute HCN half-life for smoke inhalation cyanide exposure.”

Can smoke color indicate HCN?
Absolutely not, according to Dr. Alan Hall, world renowned for his research, knowledge and expertise on the topic of HCN and other toxins:

“As both CO gas and HCN in the vapor phase are colorless, the color of the smoke is of no use whatsoever in determining whether or not dangerous levels of either toxicant are present. The more dense the smoke, most likely the greater concentration of soot, but I think you can’t say more than that.”