The external partial pressure of oxygen decreases with altitude, for example in areas of high altitude or when flying. This decrease results in decreased carriage of oxygen by hemoglobin. This is particularly seen as a cause of cerebral hypoxia and mountain sickness in climbers of Mount Everest and other peaks of extreme altitude. For example, at the peak of Mount Everest, the partial pressure of oxygen is just 43 mmHg, whereas at sea level the partial pressure is 150 mmHg. For this reason, cabin pressure in aircraft is maintained at 5,000 to 6,000 feet (1500 to 1800 m). Diving. Hypoxia in diving can result from sudden surfacing. The partial pressures of gases increases when diving by one ATM every ten metres. This means that a partial pressure of oxygen sufficient to maintain good carriage by hemoglobin is possible at depth, even if it is insufficient at the surface. A diver that remains underwater will slowly consume their oxygen, and when surfacing, the partial pressure of oxygen may be insufficient (shallow water blackout). This may manifest at depth as deep water blackout. Suffocation. Decreased concentration of oxygen in inspired air caused by reduced replacement of oxygen in the breathing mix. Anaesthetics. Low partial pressure of oxygen in the lungs when switching from inhaled anesthesia to atmospheric air, due to the Fink effect, or diffusion hypoxia. Air depleted of oxygen has also proven fatal. In the past, anesthesia machines have malfunctioned, delivering low-oxygen gas mixtures to patients.
Potassium bicarbonate (IUPAC name: potassium hydrogencarbonate, also known as potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid. Production and reactivity
It is manufactured by treating an aqueous solution of potassium carbonate with carbon dioxide:
K2CO3 + CO2 + H2O → 2 KHCO3Decomposition of the bicarbonate occurs between 100 and 120 °C (212 and 248 °F):

2 KHCO3 → K2CO3 + CO2 + H2OThis reaction is employed to prepare high purity potassium carbonate. Uses
Food and drink
This compound is a source of carbon dioxide for leavening in baking. It can substitute for baking soda (sodium bicarbonate) for those with a low-sodium diet, and it is an ingredient in low-sodium baking powders.As an inexpensive, nontoxic base, it is widely used in diverse application to regulate pH or as a reagent. Examples include as buffering agent in medications, an additive in winemaking. Potassium bicarbonate is often found added to club soda to improve taste, and to soften the effect of effervescence. Fire extinguishers
Potassium bicarbonate is used as a fire suppression agent ("BC dry chemical") in some dry chemical fire extinguishers, as the principal component of the Purple-K dry chemical, and in some applications of condensed aerosol fire suppression. It is the only dry chemical fire suppression agent recognized by the U.S. National Fire Protection Association for firefighting at airport crash rescue sites. It is about twice as effective in fire suppression as sodium bicarbonate.