Stale: no longer fresh and therefore unpleasant to eat or smelling unpleasant. Pasado. E.g. stale cigarette smoke.
Brew: /bruː/ to make a hot drink of tea or coffee. E.g. freshly brewed coffee.
Sizzle: to make the sound of food frying in hot oil. E.g. sizzling sausages.
Acrid: / ˈækrɪd/ having a strong, bitter smell or taste that is unpleasant. Pungent. Acre, fuerte. E.g. acrid smoke from burning tyres.
Rancid: /ˈrænsɪd/ if food containing fat is rancid, it tastes or smells unpleasant because it is no longer fresh. Rancio. E.g. rancid butter. Butter soon goes/turns (= becomes) rancid in this heat. There was a rancid smell coming from the kitchen.
Pungent: /ˈpʌndʒənt/ having a strong taste or smell. Olor acre. E.g. the pungent smell of burning rubber. The air was pungent with the smell of spices.
Faint: that cannot be clearly seen, heard or smelt. Débil. E.g. a faint smell of perfume.
Musty: smelling damp and unpleasant because of a lack of fresh air. Rancio. E.g. a musty room. A musty smell of old books. These clothes smell musty.
Unmistakable: that cannot be mistaken for somebody/something else. Inconfundible. E.g. Her accent was unmistakable. The unmistakable sound of gunfire.
Overpowering: /ˌəʊvəˈpaʊərɪŋ/ very strong or powerful. Abrumador, opresor, opresivo, sofocante. E.g. an overpowering smell of fish. An overpowering personality. The heat was overpowering.
Sickly: that makes you feel sick, especially because it is too sweet. Empalagoso. E.g. a sickly sweet smell.
Give off something: to produce something such as a smell, heat, light, etc. Desprender. E.g. The flowers gave off a fragrant perfume. The fire doesn't seem to be giving off much heat.