Mold in a Humidor

Should One Air a Humidor on a Regular Basis?

Almost every book on cigars, every Internet forum and even the instructions for use of a humidor include the recommendation to air the humidor on a regular basis. They give factual reasons for doing so, such as “Cigars release gases into the surrounding air … which must be cleared by airing the humidor. Only if the humidor is aired on a regular basis … can one be sure to be free of musty odours in the humidor”. If I might be permitted to say so, that is complete nonsense. The aroma of the tobacco belongs in the cigar and not in the living room. The more frequently a cigar is exposed to fresh air, the greater the loss of the bouquet. Every cigar smoker will attest to the fact that over time cigars lose their “nose”, that is the aroma that one can smell. This effect is particularly evident when the cigars are stored singly in the humidor and not in boxes. Let us begin by taking a look at the following arguments that have been used.

Cigars need Oxygen in Order to Mature – In itself that is perfectly true. If you were to store a cigar in a vacuum pack, it would mature extremely slowly and develop completely different aromas, a fact I have verified through experimentation on several occasions. To draw from this the conclusion that you should open the humidor regularly in order to let fresh air in is, however, incorrect. Even in a humidor that has been filled to its maximum capacity, there is sufficient air remaining to allow the tobacco aromas to develop positively and to avoid any danger of bitter substances, or, in the most extreme cases, putrid smells developing (such as happens when stored in vacuum packs). Here is a simple experiment you can try: take a humidor that seals well, fill it with cigars and leave it shut for the next three months. If you measure the oxygen content of the air in the humidor during this period you will notice that this falls by very little, if at all.

It is true that cigars need oxygen in order for their aromas to develop, but they do not use oxygen in the same way that plants use carbon dioxide. The cigar does not “breathe in” the oxygen, but rather releases compounds of ammonia into the air in the humidor (the gases described above) which is the cause of the stable-like smell. If the humidor remains closed, the air inside becomes almost saturated with the evaporated aromatic compounds and these evaporations are then reduced (stay in the cigar). This is commonly referred to as “reductive” storage (as opposed to oxidative storage with regular airing), although from a purely chemical point of view the term reduction is nonsensical, since no reduction occurs in the chemical sense. All that happens is that there is a reduction in the evaporation of the components which affect the aroma of the tobacco, but that is exactly what we want. The cigar should smell of tobacco for as long as possible and maintain a good presence on the nose instead of losing its bouquet steadily over time.

Preventing Musty Odours by Regular Airing – In a humidor there should be a slight “stable” smell. This is caused by the emission of ammonia compounds and is completely normal. However, a musty odour is something else altogether. If your humidor smells like a damp cellar or a wet dog there are two main causes: either the humidity levels have been too high over an extended period, possibly resulting in the growth of mould (which should not be confused with cigar bloom), or inappropriate materials have been used in the construction of the humidor (e.g. untreated MDF or hardboard surfaces in the tray or the supports for the floorboards in cabinet humidors).

If stored correctly the cigars themselves will never develop a musty odour. The reason that airing the humidor is recommended is the result, in my opinion, of two considerations: A) the fact that passive humidification systems are not able to maintain a constant and sufficiently low level of air humidity over extended periods of time, and B) the use of unsuitable materials in the construction of the humidor. In this case airing the humidor on a regular basis can prevent musty odours from forming, as it lowers the excessive level of air humidity and allows the musty odour, caused by the use of inappropriate materials, to escape from the humidor, but at the cost of loss of aroma from the cigars.

My conclusion and recommendation: An intelligently constructed humidor with a precise humidification system requires no additional airing (it is aired in any case whenever the humidor is opened). If it is possible to do so, store your cigars in their box and put the box in the humidor – that is the best that you can do for your cigars. They will maintain their bouquet for many years and will develop perfectly. If your humidor contains a tray, inspect the sides of the air holes in the base of the tray. Should these consist not of water-resistant plywood or solid wood, but reveal a homogenous, light brown surface (MDF), remove the tray from the humidor and the musty odour will be considerably reduced.

This article was published in the Cigar Journal Spring Edition 2011. Read more

Marc André is a passionate cigar smoker and humidor manufacturer. He has developed various humidification technologies for humidors, consults on and creates special humidor series and custom orders, and is in high demand as a lecturer on topics like cigar storage and humidor construction. His website,, features his 100%-made-in-Germany Century series, which offers a range of professional solutions to cigar storage – from small table humidors to aging cabinets.


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