Simatic HMI Panel PC Ex and Simatic HMI Thin Client Ex are designed for hazardous zones 1ā21 and 2ā22 and eliminate the need for complex and expensive enclosures or additional certification. Both are offered in 15-in. and 19-in. touchscreen models with eight built-in function keys. Both are suitable for applications where ignitable gases, vapors and air/dust mixtures are present.