What are the regulatory requirements by law for explosion protected
equipment in Taiwan?

According to Article 7 of “Occupational Safety and Health Act”, all explosion-protected (Ex) electrical equipment (for all Zones) shall comply with applicable safety standards specified by Ministry of Labor and complete the product safety information registration on the official web system (tsmark.osha.gov.tw) with the Safety Label marking for legal manufacturing, import lease supply and installation.
ITRI Type Verification Certificates for Ex equipment indicate conformity to the specified safety standards, and are competent and satisfactory proofs for product safety information registration.

What standards shall Ex equipment comply with in Taiwan?

Article 110 and 111 in “Safety Standard of Machinery and Equipment” specify that Ex electrical equipment in construction, performance, testing, marking and hazardous area classification shall, where applicable, comply with Taiwan National Standard CNS 3376 series (or IEC 60079 series) or CNS 15591 series (IEC 61241 series) or other relevant standards additionally designated by Ministry of Labor. Due to technical requirement variations within CNS standard series, current valid IEC standards may take precedence if the CNS counterparts are not applicable or available.

As for Article 110 and 111 in “Safety Standard of Machinery and Equipment”,
Has Ministry of Labor announced adoption of any relevant (institutional or regional) standards other than CNS or IEC standards?

No. Currently, Ministry of Labor has not announced acceptance of any relevant standards other than CNS or IEC standards for Ex electrical equipment in Taiwan. For example, EN 60079 standards for ATEX or other national/regional standards (whether harmonized to IEC standards or not) are invalid and ineffective in Taiwan.