Of the various spices that manage to please us by causing irritation and pain, the mustards and their relatives are unique in providing a volatile pungency, one that travels from the food through the air to irritate our nasal passages as well as our mouth. The active ingredients of chillis and black pepper become significantly volatile only at high temperatures, above about 140°F/ 60°C, which is why roasting hot chillis or toasting peppercorns can cause everyone in the kitchen to start sneezing. But mustard and horseradish and wasabi can get into the nose even at room or mouth temperature. Theirs is a head-filling hotness.