When a Boveda-regulated humidor fails to hold its number, the owner's first suspicion usually falls on the level chosen or on the packs themselves. Almost always, neither is at fault. The most common mistake in humidity control is not the wrong relative humidity. It is underdosing: asking one pack to do the work of two or three, and then concluding that the system does not work when it runs out of capacity in a matter of weeks.
Getting the quantity right is not complicated, but it does require setting aside one intuitive and wrong idea, which is that the number of packs should follow the number of cigars. It should follow the volume of air to be stabilised and the quality of the seal that contains it. Once that is understood, the rest is arithmetic.
What a pack is actually working on
A Boveda pack does not humidify cigars. It humidifies air, and the cigars then come into equilibrium with the air around them. The pack's task is therefore defined by the enclosure: how many litres of air it holds, how much of that air is exchanged with the room each time the lid is opened, and how much leaks through the joints and the seal between openings.
A well-made desktop humidor of the kind built for fifty cigars encloses a fixed volume whether it holds fifty cigars or five. The packs inside have the same body of air to condition either way. What changes is how much help they get, and that is where the intuition about cigar count goes wrong.
Count volume, not cigars
Cigars are themselves a humidity buffer. Fifty cigars at 69 per cent hold a good deal of water in their leaf, and they release it into the air if the interior dips and reabsorb it if the interior climbs. A full humidor is, in effect, self-stabilising to a degree; the packs correct the small drift that the cigars do not, and the whole system moves slowly.
Empty a humidor to a handful of cigars and that buffer is gone. The same volume of air now has almost nothing in it to resist a change, so every opening of the lid and every warm afternoon moves the interior further and faster, and the packs must do all of the correcting themselves. This is why a half-empty humidor asks for as much from its packs as a full one, and often more. It is also why a new collector who buys a large box and fills it slowly is the person most likely to see packs exhaust early and conclude they are faulty.
The practical rule is to dose for the humidor's built capacity rather than its current contents. A box made for fifty cigars is dosed as a fifty-cigar box on the day it is bought, whether ten cigars or fifty go into it.
A starting rule of thumb
Boveda's own guidance, and the shop's, is a reasonable starting point rather than a precise formula: one size-60 pack for roughly every twenty-five cigars the humidor is built to hold. A twenty-five-cigar desktop box takes one; a fifty-cigar box takes two; a hundred-cigar box takes four. Larger enclosures can be served with the size-320 pack, which does the work of several smaller ones and suits cabinets and large chests where space for individual packs is not a concern. The small packs are for travel cases and small boxes of a few cigars, where a size-60 would be physically awkward and unnecessary.
Two things about this rule deserve emphasis. First, it is a minimum, and it assumes a good seal. Second, more packs never over-humidify. A pack cannot push the air past its rating, so the only consequences of adding a pack beyond the guideline are that each pack works less hard and the set lasts longer. Rounding up is always the safe direction.
Adjusting for the seal
The rule of thumb assumes a humidor that closes properly: a lid that seats evenly, a lip that meets its groove, and no gaps at the hinge. Very few desktop humidors are perfect in this respect, and many are quite poor. A box that leaks exchanges its conditioned air with the room continuously, and the packs must replace what is lost as fast as it goes.
There is a simple test. Set the packs in the empty, seasoned humidor with a reliable hygrometer, close it, and leave it for two days without opening it. If the reading sits at the pack's rating, the seal is doing its share. If it settles two or three points below and stays there, the box is leaking faster than the packs can supply and needs either more packs or attention to the seal. As a general guide, a box known to be leaky should carry half again as many packs as the rule of thumb suggests, and one that is badly leaky should carry double.
The same logic applies to frequency of use. A humidor opened several times a day loses a portion of its air each time, and in a dry Canadian winter the air that replaces it may be at 20 per cent. Dose that box as though it were leaky, because in effect it is.
The cost of underdosing
A single pack in too large a volume does not hold the target a little less well. It fails in a specific and predictable way. Because the air never reaches the pack's rating, the pack never stops giving. It works continuously, at full rate, from the day it goes in. Its water is gone in a fraction of the time it would last in a properly dosed box, and the interior never reaches the number on the label at any point in that short life.
The owner, seeing a stiff pack after six weeks and a hygrometer that never read right, replaces it with another single pack and repeats the experience. Two undersized packs used back to back cost the same as two correctly sized packs used together, and they deliver a humidor that was never once at target. Two packs installed together would have shared the load, reached the number, and then idled, each releasing only what the box actually lost. Properly dosed, a set of packs typically runs two to four months depending on the seal. Underdosed, the same packs run out in weeks and achieve nothing in the meantime.
Too few packs, in other words, does not stretch the supply. It exhausts it.
Placement and replacement
Where the packs go matters less than how many there are, but a few habits help. In a desktop box, one pack on the floor and one under the lid or on the upper tray distributes the work. In a deep chest or a cabinet, spread the packs across the levels rather than stacking them in a corner; air in an undisturbed enclosure moves slowly, and a pack conditions the air nearest to it first. The packs may rest directly against the cigars without harm, though many collectors keep them slightly apart out of tidiness. Nothing needs to be wrapped, propped or protected.
When the packs go stiff, replace the whole set at once. A fresh pack placed beside a spent one carries the load alone and exhausts early, which is underdosing by another route. Never wet or refill a pack; a spent one is simply finished.
A worked example
Take a desktop humidor built for seventy-five cigars, with a lid that seats reasonably well, kept in a heated house and opened most days. The rule of thumb gives three size-60 packs. The daily opening argues for rounding up, so four is the sensible number, set two low and two high. In a house that runs very dry through the winter, a fifth would do no harm and would extend the interval between changes. Expect the set to run toward the two-month end of the range in January and toward four months in a mild, humid summer.
Compare the alternative: one pack, because the box holds only thirty cigars at the moment. It will go rigid in a few weeks, the cigars will spend that time a little dry, and the owner will have learned nothing except that they need more packs. It is a cheap lesson, but a cheaper one is to buy the right number from the start. El Laguito is an authorized Boveda retailer and is glad to work out the count for any humidor brought in or described; the only detail needed is what the box was built to hold and how well it closes.