Ventilation around switches

The primary goal of course is to have an unencumbered escape path for the warm air. Some switches can run warmer than others, but for the most part they are all resilient when the rules for each particular switch are followed. Which switch models are you referring to, and will they be racked alongside other equipment or standing alone outside a rack? The space allowed for exhaust (particularly with racked switches) generally refers to the area straight out from the fans, following between the top and bottom planes of the switch. If available, it may be a good idea to check the temperature sensors on the switches once they are in place. Hope this helps.

It could also read as needing 5" behind the switches, rather than above or below.

They are S3048-ON and S4048-ON switches. If I read the installation guide as there needing to be 5" above and below each switch, that is 7U per switch, which is a lot of rack space. If I read the installation guide as 5" diameter, from the centre of the fans, then that is 3U per switch, which isn't too bad. It allows for cable management above and below the switch. From the manual: For proper ventilation, position the S4048-ON in an equipment rack (or cabinet) with a minimum of 5 inches (12.7 cm) of clearance around the exhaust vents. When you install two S4048-ON switches near each other, position the two chassis at least 5 inches (12.7 cm) apart to permit proper airflow. The fan speed increases when the internal temperature reaches 161.6°F (72°C) and decreases to normal speed when the temperature falls to 136.4°F (58°C). The S4048-ON never intentionally turns off the fans.

It also would depend on if you have a cold aisle you are pulling air in from, ambient temperatures surrounding the switches/rack. So regardless of how they are racked, it is good to monitor all equipment (switches, storage, and servers) in a rack, in case of AC failures, modifications in airflow, etc. Tools like OpenManage Network Manager are good for getting SNMP traps from switches. You can set temperature thresholds to whatever you desire to get notified. Assuming you are using OS9, system commands like show environment, show system stack-unit 0, show alarms threshold, snmp-server enable traps, etc. allow you to enable and monitor automatically or manually to keep your normal speed under 58°C, adjusting as necessary.