Short answer: order a router that already carries the Class I, Division 2 mark, and house it in a gasketed stainless enclosure rated for your site's water and corrosion. Bring the antenna in through a sealed bulkhead feedthrough. The enclosure never approves the radio — a sealed box around ordinary gear is still ordinary gear in a classified area. Three ways in, in order of preference: a radio certified for Division 2, a general-purpose router with no arcing parts and a datasheet surface temperature under the gas limit, or a purge system to NFPA 496. Heat decides the last check. A 20 W radio in a 24 x 20 x 8 in stainless box adds about 5 K, and 35 °C outside becomes 40 °C at the radio — the ambient most electronics stop at.
The three ways a router gets into Division 2
Start with the equipment, because the location approval lives there.
A radio marked for Class I, Division 2 is the clean path. The mark names the gas groups it covers and a temperature code, and its installation documents tell you which entries need seals. The enclosure you buy handles the environment — hose-down water, salt air, washdown chemicals — because the Division 2 approval rides on the radio itself. A plain junction box in the same area turns on the same question of which rating lives on the equipment and which on the box, as whether a NEMA 4X junction box is enough in a Class I Division 2 area works through.
An ordinary router can still qualify. NEC's Division 2 rules permit general-purpose equipment under two conditions: normal operation must produce no arc, spark or hot surface able to ignite the gas, and the surface temperature must stay below that gas's ignition temperature. OSHA's electrical rules for hazardous locations list the nonincendive-circuit technique — equipment that cannot release enough energy in normal operation to ignite the gas — as permitted for Division 2. The path needs a published surface temperature, and consumer radios rarely print one, so for most off-the-shelf gear it closes itself.
The third path is the purge. A sealed enclosure with pressurization to NFPA 496 makes the inside of the box an unclassified space. The Division 2 version is a Type Z purge: clean instrument air in, with a pressure switch and an alarm watching it. Power goes on only after the purge cycle proves clean air, and the switch drops it on loss of pressure. It is the standard answer when the plant insists on a specific uncertified radio or PLC, and what to specify in a Class I Division 2 purge kit lists the parts.
What the enclosure itself must carry
Division 2 rarely needs a box built to contain an explosion. Enclosures marked for Class I, Division 2 exist, and they bundle a water rating such as Type 4X with the location approval from a hazardous-location maker. A Type 7 enclosure is the heavier Class I Division 1 design: it withstands an internal explosion and cools the flame before it exits. In a Division 2 area you normally satisfy the location through the equipment's certification or a purge, and the box carries the environmental rating.
We build the environmental half, never the hazardous-location half. Our stainless enclosures are rated NEMA 4X / IP66 by the manufacturer, not UL listed, and we do not build hazardous-location enclosures. Around a certified radio, a custom 316L stainless box with your cutouts is the shell that keeps washdown water and salt off the electronics. We build it from your drawing and deliver it in 10 business days. Where the site demands listed equipment, our box cannot be that listing — the UL 50E and NEMA 250 listing guide explains who lists what, and the approval path for an unlisted enclosure walks the conversation that follows.
The temperature code and the gas
The gas sets the ceiling, and the temperature code names it. Every certified device in a Class I area carries one: the maximum surface temperature it may reach. NEC and IEC 60079 share the same table.
| Code | Maximum surface temperature |
|---|---|
| T1 | 450 °C [842 °F] |
| T2 | 300 °C [572 °F] |
| T3 | 200 °C [392 °F] |
| T4 | 135 °C [275 °F] |
| T5 | 100 °C [212 °F] |
| T6 | 85 °C [185 °F] |
Read the gas's ignition temperature off the area's classification drawing and pick the code whose temperature sits below it. A solvent vapor that ignites near 340 °C needs a marking at or under T2 (300 °C). The code then holds only inside the ambient range the datasheet prints. A T4 mark earned at 40 °C ambient does not carry to 55 °C air — run the radio past its rated ambient and the marking has nothing under it. That is why the box's internal temperature, worked out below, is part of the approval rather than a comfort detail.
Sizing the heat margin for a 24 x 20 x 8 in box at 35 C ambient
Inputs. The radio draws 20 W — a hypothetical worked-example input, and the one to replace with your datasheet's worst case. PoE budgets give the range: an IEEE 802.3af port delivers about 13 W to the device, an 802.3at port about 25 W. The box is a sealed stainless wall-mount enclosure at 24 x 20 x 8 in [610 x 508 x 203 mm] with no vents. The wall value is k = 3.7 W/m²K for stainless, this site's sizing reference, and the site ambient is 35 °C.
Rule. A sealed box sheds heat through its walls at k x A x (T_inside - T_outside). Solved for the rise, ΔT = Q ÷ (k x A).
Arithmetic. Wall area: 2 x (24 x 20) + 2 x (20 x 8) + 2 x (24 x 8) = 960 + 320 + 384 = 1,664 in² = 1.07 m². Wall conductance: 3.7 W/m²K x 1.07 m² = 3.97 W/K. Temperature rise: 20 W ÷ 3.97 W/K = 5 K.
Result. About 40 °C at the radio on a 35 °C day.
Decision. A radio rated to 40 °C ambient — the standard limit for drives and most electronics unless the datasheet allows more — sits exactly at its limit with nothing in reserve. At the top of an 802.3at port, 25 W, the rise reaches 6.3 K and 41.3 °C inside. A 24 x 24 x 10 in box sheds more: 1.36 m² of wall gives 5.04 W/K, so the same 20 W rise falls to 4 K, about 39 °C inside. Past 35 °C site ambient, the purge air does the cooling: continuous-flow purge carries the heat out with it, or you fit a cooling unit certified for the location. Confirm the internal ambient stays inside the radio's rated range — that is what keeps the temperature-code mark standing. Sizing a non-ventilated stainless enclosure by heat dissipation walks the same arithmetic for any box.
Cable, coax and antenna entries
The entries follow the equipment documents, not habit. Where the radio's certification calls for a seal, you fit a listed sealing fitting and fill it with the sealing compound its marking names; potting compound by itself is not a listed cable entry. Division 2 asks for seals only where those documents call them, so the radio's and antenna's instruction sheets are the list you build from.
The antenna is equipment in the classified area too, and you pick the layout by RF plan as much as by code:
- A certified antenna stays in the area, mounted on the enclosure or a nearby mast, with the coax entering through a bulkhead feedthrough that preserves the enclosure's water rating.
- An ordinary antenna moves outside the Division 2 boundary, and coax runs from the radio to it. The wall entry still needs the sealed feedthrough — sealing an outdoor antenna feedthrough shows the fittings that hold the rating — and planning the RF path in a radio enclosure covers coax length, grounding and placement.
Ground the coax at the entry either way: a surge coming down the antenna line should land on the box wall, not on the radio board.
What to put on the order
Your environment picks the shell and your gas picks the approval. Wet washdown or salt air takes a 316L stainless box; a dry indoor corner takes 304; an uncertified radio takes the purge package on top of either. The order reads like this:
| Line | What to order | What it covers |
|---|---|---|
| Radio | Marked Class I, Division 2, gas group per the classification drawing, temperature code stated (T4 caps the surface at 135 °C) | the Division 2 approval |
| Enclosure, wet or corrosive site | Custom 316L stainless box, Type 4X water rating, cutouts for the glands and the bulkhead feedthrough, built from your drawing and delivered in 10 business days (the custom enclosure builder) | water, hose-down, corrosion |
| Enclosure, dry indoor site | 304 stainless with the same cutouts | everyday industrial duty, washdown-capable shell |
| Purge, only for an uncertified radio | Pressurization to NFPA 496, Type Z, with clean air supply and a pressure switch that alarms | Division 2 to unclassified inside the box |
| Entries | Certified cable glands; listed sealing fittings filled per their marking where the radio's documents call them | rating and approval together |
| Antenna | Certified antenna in the area, or coax through a sealed bulkhead feedthrough to an antenna outside the boundary | the antenna's own approval |
The enclosure never carries the Division 2 approval on its own. Put the approval on the radio or on the purge, put the water rating on the box, and the order closes cleanly.
Questions
Does a sealed enclosure give an ordinary router a Division 2 rating?
The box earns the water rating and the radio earns the Division 2 approval; no enclosure hands its rating to the gear inside. Three compliant paths exist: a radio marked for Class I, Division 2 with its gas group (A through D) matching the classification drawing, a general-purpose router with a datasheet surface temperature below the gas's ignition temperature, or a purge system to NFPA 496. Certified radios carry a temperature code such as T4, which caps the surface at 135 °C.
What temperature code does the radio need for a Division 2 area?
Take it from the gas on the classification drawing: the code you can carry is the one whose temperature sits below the gas's ignition temperature. The table steps from T1 at 450 °C down to T6 at 85 °C, and methane, which ignites far above 450 °C, lets equipment run at T1. A radio marked T4 caps its surface at 135 °C, and the mark holds only inside the datasheet's ambient range.
Where does potting compound fit in the cable entries?
Sealing fittings are listed assemblies filled with the sealing compound their marking names; bare potting compound alone is not a listed cable entry. In Division 2 you fit seals where the radio's and antenna's installation documents call for them, and each sealing fitting takes only the conductor fill its marking allows.
Does the antenna need its own approval?
Yes when it lives inside the classified area: it is electrical equipment there, so it rides the radio's certification or carries its own mark for the location. The alternative is mounting it outside the Division 2 boundary and running coax back through a sealed bulkhead feedthrough, with the entry grounded so a lightning surge lands on the box wall rather than the radio.
How much heat can a sealed stainless box handle before the radio runs past its rating?
A 24 x 20 x 8 in stainless box rejects about 4 W per K: 1.07 m² of wall at 3.7 W/m²K sheds 3.97 W for each degree of rise. A 20 W radio adds about 5 K, so 35 °C outside becomes 40 °C at the radio; at 45 °C outside the same box runs near 50 °C inside, past the 40 °C rating most electronics carry.
