For example, I had a lady call and tell me all of her beautiful Cattleya blooms had just died for no apparent reason. When I went to her home I found a basket of apples that she was going to can. Once the orchids was removed from the room the blooms that were left did not die. Ethylene gas is also a component of smog. If you live in a very smoggy area, you may want to keep your windows closed on the days of high air pollution.
Sepal wilt is an ailment that affects many types of orchids.
Sometimes before the buds have a chance to open they wither and drop off the plant, sometimes they open but the sepals turn papery and become brown or black at the tips. Other orchids that are effected are Vandas, Laelias, Catasetums, Stanhopeas, Cycnoches, Cymbidiums and Maxillarias. If your blooms suddenly wilt and turn brown, check the quality of the air in the area where they are growing. And make sure you don't have a basket of apples sitting around. You should never smoke around your orchids.