Ocenair screens and noseeums

[nuru05]

Does anyone know if the ocean air screens will block noseeums? Or if not is there a similar type of rolling screen that will?

[GordMay]

The number of openings is the mesh size. The size of openings [in μm] is the free area, between wires.
So, a 4-mesh screen means there are four little squares, across one linear inch of screen. A 100-mesh screen has 100 openings, and so on.
As the number describing the mesh size increases, the size of the particles decreases. However, mesh size is not a precise measurement of the mesh opening size. This is because screens can be made with different materials, with different thicknesses of strands or wire. The thicker the strands, the smaller the openings that a particle can pass through, and vice versa.
Micron [μm] rating is used to define wire mesh openings, with an opening size smaller than 1 millimeter. It is defined as the precise distance between the wires, of any opening.

IIRC, standard no-see-um screening is 20 mesh, or 840 μm [0.84mm, or 0.033"] opening size.

[deltaten]

Just a bit of anecdotal data for you....
As mesh size decreases, airflow drops proportionally.
I use sorta standard camping- type double knit no-see-um screening on my fwd hatch and companionway when bugs are bad. Fan is typical 20" box fan bungee'd in 20" fwd hatch. Scree ing reduces airflow by 50+%

Just FYI

[MicHughV]

There is one simple way to deal with noseeums.

That is "skin so soft" hand lotion. You can spray this on exposed arms, legs, etc, and noseeums simply drown in the stuff, should they land on you. Some people mix it with water and have a handy spray bottle handy.

I've found that noseeums tend to hang outside the boat, and rarely come inside a boat. Why this should be so, I don't know.