Why is the tested ambient temperature of the wifi model lower than the non-wifi model? They both use the same processor!
RB4011iGS+5HacQ2HnD-IN Tested ambient temperature -40°C to 45°C
RB4011iGS+RM Tested ambient temperature -40°C to 70°C
Same test
L009UiGS-2HaxD-IN Tested ambient temperature -40°C to 70°C
L009UiGS-RM Tested ambient temperature -40°C to 70°C
Heat dissipation of Wifi chips doesn’t count ? (RB4011 has 2 different ones, one for each radio)
It needs to go somewhere …
On L009 thermal management is done completely different (and only 1 wifi radio), hence most likely the same values for Wifi and non-wifi version.
Thanks
My question is whether I can use it in an environment that can reach up to 50 degrees.
When vendor provides some information, then it most of times means something. If MT says that wifi variant of RB4011 works in ambient temperatures up to 45°C, then it means it's likely that device will survive for a decently long time. Of course you can operate it (it's your device, you've paid for it) at ambient temperature of 50°C ... but if device cooks sooner than you'd like, then it's your loss.
That was not your initial question in your first post.
You asked why they have different specs.
This is another one, this is if it can work in a temperature slightly higher then specified.
Considering safety margins usually applied when determining such limits, it will most likely simply work just fine ( with possible reduced lifetime but no clear way to determine by how much).
But I would make certain there is enough airflow to help keeping those limits not too far away.
The problem of high ambient temperatures is that this means higher temperature of internal components. And higher component temperature means faster aging … so even if device doesn’t die immediately it may die “of old age” prematurely. Capacitors are specially prone to faster aging.
I know but you can never precisely calculate the effect.
Only a range with estimates.
Seen enough results of temperature testing back in the time I used to work for a multinational telco equipment manufacturer.
My question was this, but I didn’t make it clear in the first post. What I found strange is the fact that the model without Wi-Fi can handle a place with 75 degrees. In this case, would this loss to 45 degrees be only due to the Wi-Fi module? Assuming that in this case, both are the same construction?
It is currently in a ventilated rack, where it is at 37 degrees (RB4011 Wi-Fi), that is, with an ambient temperature of 45 degrees, could it reach 50 degrees?
Thank you to everyone who took a moment to respond to me!
Maison
First of all, the specified temperatures in the specification all refer to ambient temperature, that is: locate it in a normally ventilated (non-obstructed) place and put a (normal room) thermometer let’s say 30cm from it. What that reads is the temperature data sheets refer to.
Yes, the WiFi chips do cause quite a bit of excess heat. The construction of the WiFi and non-WiFi 4011’s are quite same (they even use the same PCB), but the cooling solution is far from uniform, especially because one of the WiFi modules is attached as a PCIe card, which has much worse cooling than other parts of the product. This is the cause of the severe derating.
Other than that, generally the Arrhenius equation is used for derating lifetimes. In the specs it says 200 000 hours @ 25 degC. That’s a bit over 20 years. For every 10 degC of temperature increase, halve this.
Aging (as the word itself implies) takes time. So if it’s only exposed to higher temperatures for one month of the year, that should cause no appreciable additional aging.
But with the added PCIe card, you probably chose the worst possible product Mikrotik offers for this type of situation. 
Thanks
It only has Wifi 5.8 because I use the AC drive, if I disable its wifi will the temperature tend to drop more?
Obviously, yes.
I don’t use the sfp port, if I disable it, does that also help with the temperature?
Not have sfp installed
5ghz radio is the main reason of the restricted temperature range, is a 4x4:4 wifi5 wave 2 radio so it generates a significant amount of heat, disabling radios does not ensure lowering power usage
rb4011 is a passive cooled device (entire chasis is the heatsink), because of that it has temperature restrictions
i think in your situation you must ensure active cooling (using a fan). that will be enough