What was the reason for the "black cough" of F-22 pilots?

Diisocyanates, which are found within the polyurethane glues that comprise the stealth coatings, can reportedly cause both severe lung and neurological problems.

The problem is posed by heat generated through aerodynamic friction. The RAM used by the B-2, F-117, F-22 and F-35 needs to be held in place by an adhesive. In the case of supersonic flight, temperature of the outer skin can reach over 1000 degrees at high speed.

Pierre Sprey, co-designer of the F-35 revealed: The radar absorbing coating is kept in place using an adhesive that emits lethal toxic gas while the aircraft is traveling at high speeds. Toxins were found in the blood of pilots and this issue has already has claimed the life of one pilot, Jeffrey Braden.

A technician performs maintenance on the F-35

In the event of a crash, these toxic composite materials would pose a significant health hazard within a wide radius of the crash site as the unavoidable clouds of lung-searing toxic gases and toxin-bearing fibers that would stream from burning composite wreckage for days.

The alleged “on board oxygen generating system” (OBOGS) for the F-22 seems suspicious because there is no logical need for it. The aircraft does not operate for such great duration for this to be required, nor are there any obstacles posed by the conventional oxygen supply solutions. It would be a hard bargain to offer this problem as the only culprit behind a host of health complications among F-22 pilots, many of which have resulted in death.

I've heard several versions of what caused the problem. Not sure which I believe, if any. There were problems outside of just the F-22, and I do believe that the other planes withbsimilar problems all have an Onboard Oxygen Generation System (OBOGS).

Https://news.usni.org/2017/06/28/report-congress-breath-military-aircraft-oxygen-issues

Hypoxia Threatens Navy and Air

Force Pilots, and the Threat Is Growing

4 F/A-18 Pilot Deaths Tied To Oxygen System Failures, Navy Reveals

Personally, I don't think that the root cause is fixed. I am fairly certain that a great deal of money and prestige has been invested in OBOGS technology and its often difficult to retract sales pitches. I'm not sure that the move to OBOGS was justified IN THE FIRST PLACE, and now with all of the problems that seem to follow…… certainly not!

Now, it seems that the US military is infected with an issue that crosses aircraft product lines. I hope they get it fixed soon, all of these effected planes may end up being heavily used and very much needed, very soon.

From experience with civilian commercial planes problems with breathing bleed air, if this air is drawn off At low temp, below 350–400, it may be contaminated with fumes and mist from engine oils, but hotter than this and the oil starts to burn off, adding toxic byproducts of combustion ,including little black bits and CO. The long term illness comes from inhaling CO.