Where there's fire, there's smoke...
Birds have probably THE most efficient respiratory system there is. They need this efficiency to support flight but because of it they are very sensitive to pollutants in the air so air quality is a primary concern for bird owners.
Birds are exceptionally susceptible to things like second-hand smoke, cooking fumes, gases such as carbon monoxide, volatile cleaning products, paints, varnishes, fire place fumes, dirty household air ducts, fragrances, and so forth (the list is long). All of these can lead to significant respiratory distress and some can result in death.
People are always asking about burning candles and are ANY of them safe. Well, let's take a look.
Most candles are made of paraffin wax, which creates highly toxic benzene and toluene when burned (both are known carcinogens). In fact, the toxins released from paraffin candles are the same as those found in diesel fuel fumes.
So what about soy wax? Even a candle made from “100% soy wax” must be processed with a small amount of paraffin so burning soy candles will still release small amounts of the carcinogens and toxins found in paraffin, and most soy candles on the market are not 100% soy so they still contain a high percentage of poisonous paraffin.
Then there’s beeswax candles which are becoming more popular because they are safer and burn clean (relatively speaking). For humans this is the safe option, but as with any open flame, these candles still produce smoke, and depending on what the wick is made of you still could be introducing toxins. Most wicks are made from zinc or zinc alloy, which can be quite toxic to birds when burned and yes there are paper and cotton wick options but again … they still produce smoke.
As far as carbon monoxide goes, candles are burned in the open air so there is enough oxygen to keep a candle burning and enough to avoid the production of carbon monoxide. CO is found in fumes produced when you burn fuel in cars or trucks, small engines, stoves, lanterns, grills, fireplaces, gas ranges, or furnaces. CO can build up indoors and poison people and animals who breathe it.
Bottom line is that the only really safe candle is a flameless candle. They are just as pretty and a whole lot safer for you AND your pets.