arpadveress 
Who is he / she?
First a designer shall be a designer of a discipline like electrical, mechanical, fire safety, HVAC, technology, machinery, etc.
A designer shall be a member of technical chamber of a country. Registered there, and maintain his/her competencies.
As an Ex designer he/she shall be competent in terms of explosion protection / HAZLOC / Ex compliance engineering – IEC 60079-14 says:
Designers (design and selection)
Designers shall possess, to the extent necessary to perform their tasks, the following:
a) detailed knowledge of the general principles of explosion protection;
b) detailed knowledge of the general principles of types of protection and marking;
c) detailed knowledge of those aspects of equipment design which affect the protection concept;
d) detailed knowledge of content of certificates and relevant parts of this standard;
e) understanding of practical skills for the preparation and installation of relevant concepts of protection;
f) detailed knowledge of the additional importance of permit to work systems and safe isolation in relation to explosion protection;
g) detailed knowledge of the particular techniques to be employed in the selection and erection of equipment referred to in this standard;
h) general understanding of inspection and maintenance requirements of IEC 60079-17.
Very important sayings above – let us go into details:
Designers (design and selection)
Designers shall possess, to the extent necessary to perform their tasks, the following:
a) detailed knowledge of the general principles of explosion protection;
— detailed knowledge of Ex (…)
b) detailed knowledge of the general principles of types of protection and marking;
— deatiled knowledge of Ex (…)
c) detailed knowledge of those aspects of equipment design which affect the protection concept;
— full and complete understanding of Ex from manufacturer point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
d) detailed knowledge of content of certificates and relevant parts of this standard;
— full and complete understanding of Ex from certification body point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
e) understanding of practical skills for the preparation and installation of relevant concepts of protection;
— full and complete understanding of Ex from installation / commissioning point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
f) detailed knowledge of the additional importance of permit to work systems and safe isolation in relation to explosion protection;
— full and complete understanding of Ex from installation / commissioning point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
g) detailed knowledge of the particular techniques to be employed in the selection and erection of equipment referred to in this standard;
— full and complete understanding of Ex from installation / commissioning point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
h) general understanding of inspection and maintenance requirements of IEC 60079-17.
— full and complete understanding of Ex from operation / maintenance / repair point of view – what will be / has been delivered and how Ex works there for total lifetime of the site (…)
The Ex designer is the one being responsible for 1) the Ex Design Chapter (EDC), which is the basis of all other design areas such as electrical, mechanical, HVAC, fire and worksafety among others; 2) the Verification Dossier, which is like the basic setup for Ex lifetime tracking. Actually he/she does define the basics of Ex operation.
An important role and projectowner shall always check whom to work with. The Ex competence of the Ex designer is the basis of the later operation. The different disciplines shall act together using the same words for Ex compliance.
Keep up the good work!
