Ventilation And Air Movement

06/09/2020

Besides right temperatures, humidity and hydration, the air quality is one of the key abiotic factors influencing comfort and quality of life of the chameleons in the wild and consequently, it is a crucial vital factor in chameleon naturalistic husbandry.

WILD
Chameleons are in the wild exposed generally to airy biotopes where air movement is normal.
It varies from almost steady in the grass and rainforest undergrowth, inhabited either by juveniles or by some species, especially the stumptail chameleons, to very windy on the mountains, inhabited e.g. by montane, forest-edge species.
The intensity of air movement and winds varies:
Geographically
Seasonally
During the daytime and nighttime
And in dependence on biotope and microbiotope.

The air movement intensity is as a rule in the wild much higher than people imagine. A simple example of a situation is a wind with the speed of only 10cm (4in) per second. It is so slow that we would merely feel and measure it. But such wind, will exchange the full content of one cubic meter (a cube with the side size of 1m - 3,28ft) cage in seconds, it means 6 times in a minute!

Knowledge of wind intensity in the biotopes of individual species is then crucial for simulating the correct airflow in the cage.

CAPTIVITY
In captivity, there are two aspects of air movement to be considered:
THE VENTILATION - the air exchange between the cage and the space around
THE AIR MOVEMENT - the airflow within the cage.

The crucial task is to solve a heavy paradox: there is namely a following antagonistic conflict of two interests:
FACILITATE GAS EXCHANGE - make sure that fresh air in entering the cage and old gets out
MAINTAIN THE AIMED PARAMETERS OF THE AIR INSIDE OF THE CAGE - keep mainly proper ambient temperature, air humidity but also ionization, content of ethers, content of gases produced by plants etc.

There is hardly any hard rule that can be calculated or enforced. The principle is to empirically get a guideline what works in captivity.
SIZE MATTERS - Experience shows, a free space of a size of a room (approx 20-30 m3) does not require almost any intense ventilation, just air movement.
The free indoor roaming of chameleons does not require any additional air movement. The downside of this method, which is quite rare and frankly not really recommended (to be fully functional, it is very expensive) is inability to maintain higher air humidity levels, especially at night. Also, the risk of injury, escape, uncontrolled UV exposition and problems with feeding make it very problematic. Outdoor free roaming is almost impossible due to predation risk and is almost never practiced.
The smaller the cage is, the more important is the gas exchange and the bigger is the proportion of the ventilation areas on the surface of the cage.
The smallest cages should be (almost) fully from mesh to avoid any problems.
The mostly used cages for regularly kept species are around ¼ - ½ m3 big in volume.
They are also recommended to consist of mesh only. If not possible, the safest recommendation is:

SIMPLIFIED RULE
"Minimum the top and one full side should be mesh", which is a minimum limit requirement to be easily remembered.

Actually, respecting the cage construction features, especially when utilizing the "chimney effect" the real rule is:

PRACTICAL RULE
"Top from mesh plus the total area of ventilation openings should be 8-10% of the total area of the sides". Practically it allows to work with either one side or one door or several smaller openings, mainly in the lower part of the cage.

These rules work in the both cases of today's popular cage formats:
"CHIMNEY" - with the largest side oriented vertically
and
"SQUARE SHAPE" - with the two largest dimensions (almost) equal to each other oriented one vertically and one horizontally.

MESH SIZE MATTERS
Not to ignore is also the mesh structure. Normally, the window mesh or mosquito mesh is used for the cages as a rule to fulfill four functions at once:
- Permeability for air
- Safety against external
- Intruders (insects, predators, rats...)
- Safety against escape of the feeders outside the cage
- Safety against escape of the kept animal(s)
- Providing of fresh air capable of exchange and flow

The issue is, it is penetrable by air but not as simply as the mesh types with big openings with holes 1cm to 2cm big. They provide great ventilation but are not safe against the escape of the insects nor do they prevent some unwanted pests (such as ants) to enter.
The fine mesh is also very dangerous if exposed to the direct sun. As providing a limited gas exchange, it can get heated to many degrees above the ambient temperature and cause death of the chameleons inside.
Little stripes covered with perforated aluminium stripes is extremely ineffective. The air is just extremely slowly sucked inside through it. If a fan is directed against it, it almost leaves no air through as the streams of air directed towards the solid part of the perforated aluminium stripe redirect the ones that would potentially penetrate the small openings and bend them away.

VENTILATION
can be facilitated by the following means:
1. Mesh of various opening size. The air penetrates and leaves the cage through the openings passively.
2. Construction - chimney effect. The s.c. chimney effect is the movement of air into and out of the cage, resulting from air buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature, pressure and moisture differences.
3. Heating through lights. The residual or purposeful heat from light/heat sources forces air flow by two mechanisms. First, the heated air expands and creates overpressure that is set back to normal by the air leaving the cage through the ventilation openings. Second, the heated gas is less dense and therefore lighter than the colder one, thus it rises up and leaves the cage through the ceiling. The created underpressure is set off by the colder lower air layers sucked in through the ventilation openings.
4. Forced air flow - external fans. External fans blowing air against and along the cages force the air also to leave and penetrate the cages, utilizing the above mentioned effects combined with the mechanism of vacuum pump.
5. Forced air flow - peripheral fans. Small fans placed on mesh and blowing the air outside of the cage or inside can intensify the air flow as required and compensate eventually the insufficient size of ventilation openings.

AIR MOVEMENT
all the above mentioned mechanisms of ventilation course not only the gas exchange but also facilitate a certain intensity of air movement within the cage. If it is not sufficient, it can be increased by the mentioned mechanisms or enhanced additionally by
6. Forced air flow - internal fans. Small fans placed in the cage blowing the air within it, can intensify the air flow as required and even simulate wind, required e.g. by some montane species.

Remember:
ventilation and air movement is a crucial vital factor contributing to welfare of the chameleons in captivity and also an important aspect of the naturalistic chameleonoculture.