I am currently renting a flat, which prevents me from making modification to the walls. However, I still would like to run ethernet cables between rooms. Between all the rooms, there are AC vents connecting them together. Assuming that the ducts are simple air ducts without any moving parts inside (need to check), would a normal ethernet cable "survive" the conditions? I think the maximum air temperature would not exceed 60 degrees celsius.

Lastly, the the building is located in Spain.


Outdoor rated cat5/6 has temperature ranges from -5 to -15 F to 160-170 F. I know that I have seen cable ran through commercial ducts. Do I know if it passed local inspection? No.

That being said a home duct would come no where close to 150 degrees F - not talking about duct work from ovens. I guess you would worry about the casing becoming soft and sticking to the duct. I don't see the fire hazard though.

Basically the issue is - is this code or law abiding where you live? In the US that is a no. I don't know about other countries though.

I was just answering the question asked. Not trying to start a controversy - would I run it in my home through ducts? No. If I did I would use a variant of fireproof cat5.

  • Also if the venting is purely for AC, I do not see any issue with this at all. – DMoore May 14 '13 at 14:57
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    Says the person who hasn't had a building catch on fire. – Fiasco Labs May 14 '13 at 15:21
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    The big issue isn't during normal operation. The dangers come if there's a fire in the building. Codes are typically "minimum" safety rules. They don't make codes just to be jerks, there are reasons behind every code. – Tester101 May 14 '13 at 15:26
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    Let me relate how important this is. My workmate lost her two daughters and their friend to a very simple little issue. Not cables in a vent, but PVC plastics all the same. They had a sleepover and decided to stay in the small travel trailer. They had candles. The candles caught the frilly plastic curtains afire while they were asleep. It was the only damage to the trailer. They all died from asphyxiation, it was determined, due to the smoke. PVC plastics are very lethal. Having it circulating in your HVAC system may be the difference between making it out or being overcome. – Fiasco Labs May 14 '13 at 15:28
  • Personally, I've run phone and coax TV cable through air vent. There are all pre-terminated(with ends already on them) and once a year we'll cycle through them, we have 4x 20ft runs and have one extra cable so we can "swap" them, we attach a rag and pipe cleaner and use them to clean the vents, we randomly did this one time and noticed the amount of dust that collects in the duct let alone is attracted to the cables so we made it a normal thing to do. We did that for about 7 years without problems in Florida Heat. Recently a hurricane ripped the side off the house so we rewired properly then. – Jason May 14 '13 at 15:51

No you cannot. This is a code violation.

Furthermore, your insurance company can take this as a willful violation and deny a claim.

You can use the cold air return ducts, but you must use plenum rated cable.

  • I've seen the linked question and I am not in the US - possibly this may be legal in the EU? Also, treating this as a more abstract problem - would normal cables physically withstand the conditions? I am thinking that outdoor-rated cable must be fine.. – petr May 14 '13 at 14:16
  • I'm not sure you can/should run it in the return "ducts" either. It's a fuzzy code section. – Tester101 May 14 '13 at 14:18
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    @petr Code or no code, this is not a good practice. – Tester101 May 14 '13 at 14:20
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    Plenum rated cable has Fluoropolymer based insulation and is therefore more expensive, flame resistant and generates less noxious gasses when in the presence of fire. Standard cable PVC insulation is basically candle wax when on fire, candle wax that generates phosgene like gasses, like the stuff used in WW-I and is deadly to breathe. – Fiasco Labs May 14 '13 at 15:18
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    @FiascoLabs "less noxious gasses", does not put my mind at ease. – Tester101 May 14 '13 at 15:27

This is a bad idea as everyone has mentioned already. Search for "cable raceway" and your problem of aesthetics and cable management are solved without violating your agreement with the landlord.

  • although there is still the main problem - running cable between rooms with doors... – petr May 15 '13 at 15:02
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    Just run the cable under the bottom of the doors. The raceways stick to the walls so the cable will be hugging the wall and only exposed the width of the door frame. Easiest option would be wifi. – TugboatCaptain May 15 '13 at 23:52
  • Will see how it works - I think my door are actually fitting very well and may not have a gap :). Wifi just wouldn't cut it, I need the full gigabit transfer speeds... – petr May 16 '13 at 7:43

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