CMDDA1 – CO/CO2 Atmosphere & Appliance Testing


This gas safety assessment is designed to test the competence of an operative in determining ambient levels of CO and presence of CO2 in dwellings and identifying the cause of fumes using a portable electronic combustion analyser. This will typically be any engineer who responds to the genuine report of a CO alarm being activated or a report of fumes.

The scope of the assessment covers Type A, B & C domestic gas appliances fitted in dwellings and follows the guidance and procedures outlined in BS EN 7967 Part 1 to 4. Further guidance has also been issued by HSE in the form of HSE Guidance Notes HSE (EH)40 and HSE(L)56, Gas Safety (Installation & Use) Regulations. Further guidance is expected from IGEM in the near future.

It does not covercommercial premises and appliances or the procedures to adopt following an incident reportable under RIDDOR. Where an engineer is required to carry out a formal CO incident investigation on behalf of a gas supplier as part of their obligation under gas safety legislation, the engineer would need to have successfully achieved a relevant qualification in the investigation of CO poisoning and carry out the investigation in accordance with the Institution of Gas Engineers and Managers (IGEM) Industry Standard (IGEM/GL/8).

CMDDA1 – CO/CO2 Atmosphere & Appliance Testing

Course content:

The course covers the following units, plus a group of optional units:

Carrying out AmbientCO, CO2 testing and combustion performance analysis using electronic portable gas analysers on domestic gas appliances in dwellings following:

  • indication of fumes
  • smells
  • spillage or leakage of combustion products
  • CO detector activation
  • Interpretation of results and responses from householder or other party


Entry Requirements:

CCN1/CCLP1 + CPA1) or CCN1/CCLP1 as from 1st April 2012 or valid equivalent NVQ or QCF qualification + appropriate domestic appliance(s). This would have an equivalence to Level 3 qualifications.


Method of assessment:

Assessment is carried out using a variety of assessment methods including multiple choice, short written response and scenario questions and observed practical assessment.



City & Guilds CMDDA1 – CO/CO2


Duration of course

Up to 12 months


Attendance Options


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