posted 02-08-2014 09:34 PM               

1975 July 24: gas poisoning on board: During final descent and parachute deployment for the Apollo Soyuz Test Project Command Module, the U.S. crew were exposed to 300 µL/L of toxic nitrogen tetroxide gas (Reaction Control System oxidizer) venting from the spacecraft and reentering a cabin air intake. A switch was left in the wrong position. 400µL/L is fatal. Vance Brand's heart stopped and he was narrowly resuscitated. The crew members suffered from burning sensations of their eyes, faces, noses, throats and lungs. Thomas Stafford quickly broke out emergency oxygen masks and put one on Brand and gave one to Deke Slayton. The crew were exposed to the toxic gas from 24,000 ft (7.3 km) down to landing. About an hour after landing the crew developed chemical-induced pneumonia and their lungs had edema. They experienced shortness of breath and were hospitalized in Hawaii. The crew spent two weeks in the hospital. By July 30, their chest X-rays appeared to return to normal except for Slayton; he was diagnosed with a benign lesion unrelated to the gas exposure which was later removed.

posted 02-09-2014 01:20 AM               

In the former publication p.99 there is also the following information:

Physicians later theorized that Brand´s fainting may not have been related to the gas.Instead it may have been caused by temporary low blood pressure — called orthostatic hypotension — which many astronauts have experienced, though less seriously. It comes from the sudden change from weightlessness in space to exposure to the normal pull of the gravity of the Earth, or the force equal to several times that normal pull which is generated by deceleration during reentry.