Osmium metal is very stable in air, with a melting point of 2700°C, it is insoluble in ordinary acids, and will not be corroded even in aqua regia. However, powdered osmium is gradually oxidized at room temperature to form osmium tetroxide. Osmium tetroxide melts at 48°C and boils at 130°C. Osmium vapor is highly toxic and can strongly irritate the mucous membranes of the human eye, causing blindness in severe cases.

Osmium can be used as a catalyst in industry. When synthesizing ammonia, if osmium is used as a catalyst, a higher conversion rate can be obtained at a lower temperature. If platinum is mixed with a little osmium, it can be made into a hard and sharp scalpel.
Osmium-iridium alloys can be made by using the same amount of iridium as osmium. The silver-white dot on the nib of the iridium pen is osmium-iridium alloy. The osmium-iridium alloy is hard and wear-resistant, and the iridium nib is more durable than ordinary steel nibs. The key lies in this "small dot". Osmium-iridium alloys can also be used as bearings for clocks and important instruments, which are very wear-resistant and can be used for many years without damage.