# T4 — North American vs IEC/ATEX explosion protection designations

For T4, category is temperature code; maximum surface temperature (c) is 135; basis or note is Ignition temperature of gas / dust >135-200, recorded from its source on 2026-08-06.

- **Category:** temperature code _(our reading, not quoted from the source)_
- **North American designation:** T4 _(verified: appears in the quote below)_
- **IEC / ATEX designation:** T4 _(verified: appears in the quote below)_
- **Maximum surface temperature (C):** 135 _(verified: appears in the quote below)_
- **Basis or note:** Ignition temperature of gas / dust >135-200
- **Maximum surface temperature (F):** 275 _(per ldpi-inc.com, not stated by the source above)_

## What the source says

> 135 | T4 | >135-200

## What ldpi-inc.com says

> T4 | T4 | 135 | 275

Source: https://ldpi-inc.com/resources/classification-codes/class-1-locations/

## What inframena.com says

> T4 | 135°C |

Source: https://www.inframena.com/hazardous-area-classification-equivalency-guide/

## Source

- https://www.e2s.com/guide-for-hazardous-areas/gas-and-dust-groups
- https://ldpi-inc.com/resources/classification-codes/class-1-locations/
- https://www.inframena.com/hazardous-area-classification-equivalency-guide/

Last verified: 2026-08-06. Review by: 2028-08-05.
Part of [North American vs IEC/ATEX explosion protection designations](https://referencesource.org/ex-classification-system-crosswalk/).