Yes, with certain things in mind, it is possible to connect several fans to one fan header.
The most important point to consider is the collective current draw of the fans used.
The maximum input current for a specific fan can be found on the product page on our website in the "Specification" section.
Next, add up the maximum input current for all the fans that you want to connect to one fan header, and make sure that it stays below the specified maximum current for the fan header that you intend to connect them to. Most motherboard fan headers support up to 1A; this information can usually be found in the motherboard manual.
Here's an example:
Let's say you wish to connect three NF-A12x25 PWM fans to one fan header, and want to make sure that it's safe to do so.
The motherboard manual states that the fan header that you want to use supports up to 1A.
As stated in the NF-A12x25 PWM's specification, one fan draws up to 0.14A. Three fans therefore draw up to 0.42A (3 x 0.14A), which is well below 1A and therefore safe to do.
How to connect several fans:
To connect multiple fans onto a single fan header, you can use Y-cables (NA-YC1). Multiple NA-YC1 cables can be daisy-chained to control more than two PWM fans via a single fan header.