Hi all~
I’m working on a consumer electronic product, and are doing some detailing on the ventilation holes. From my (vague) memories someone mentioned that there are regulations as to the minimum/maximum dimensions these holes can be.
I’ve tried some googling, but most of the return hits pertain to building regulations. Anyone has any idea where I can find information on this?
Thanks!
It all depends on various factors:
Do you need UL/CSA/CE or other approval?
What parts are accessible through the ventilation holes? If there is nothing dangerous (ie, line voltage connections, sharp fan blades), then it is probably not necessary to make the holes any specific size.
I recommend obtaining the standards for your product or contacting your engineer(s) for standards.
There are no regulations per se, it depends on EMC and IP: electromagnetic compatibility and ingress protection.
Slots and holes should be sized relational to major frequency the device is operating at. Generally speaking 12mm is a maximum width or diameter, but for a slot’s length as well as the length to width ratio is important. On numerous projects I usually use 6 - 10 mm and as tight a periodicity as can be punched.
Ingress protection has to do with safety and is tested with a defined articulated digit simulating a human finger.
There is a lot of information available including simple formulas to use.
I would think it all comes down to the necessary airflow you need to maintain a safe operating temperature for the electric components inside the housing.
A mechanical engineer can easily help you there since they are well versed in thermodynamics.
Thanks guys for your responses! 
In this product, the concern is not so much about the ventilation issue - it’s more of the “some guy told me something about regulations saying that you shouldn’t be able to drop a standard-sized coin (in that country) into the holes”. So I guess it leans more towards ingress protection: protection against coins (!?!?) instead of finger digits. Though I’m entirely unsure whether the coin-test really exist.
I remember some guideline similar to the coin thing from my school mass production class too. dont have the book handy but remember a point about the vent holes being smaller than a pencil so you cant poke into important bits on the inside.
R
you should probably look at the two digit IP (ingress protection) rating, (European Standard EN 60529), there may be a US equivalent. The numbers refer to the protection provided against ingress, the first with respect to solid objects, the second against ingress of water. You can go for a ‘0’ in the second column (non-protected)
there is also a standard for the deign of electronic equipment (I don’t know the number sorry) which will probably cross reference the IP standard.
and as nydesignguy suggests tie this in with your thermal requirements
The coin test that I am familiar with is in relation to conductive metal components. i.e. charging pads. If a coin span the gap between positive and negative on your charging connector…that’s bad. Means dumbass will put a coin to it and short it out. If the charging connectors are connected to A/C…that could give someone a nice how do you do.
Just a few last words on vents…
The vent holes need to have a total area large enough to give the desired flow rate. The temptation is always to stack holes (or slots) as close together as possible, but the strength of the panel or product case can be reduced condiderably. There’s a trade off, as usual. More stiffness can be introduced by uing louvers if the case is sheet metal (microwave ovens, clothing lockers etc) but the appearance needs careful thought.
Europe and the USA use different standards for ingress protection. In Europe/UK, the relevant standard is EN60529 (classifies degrees of protection provided by enclosures, in other words the ‘IP’ rating). In the US, the standard is NEMA 250. Note that these standards describe how well the enclosed equipment is protected, they are not user safety standards.
As a general guide, inquisitive fingers can be denied access by a hole of not more than 7.5mm diameter (or 3.5mm diameter for infants and children).
If you can’t find the data,visit design-bites.com. NEMA and IP rating tables are in a booklet entitled Design Directions. Access hole sizes are in the booklet ‘Human Factors and Aesthetics’. They’re downloadable if you have a PayPal account (or a credit card).