Occupational Health & Safety Requirements in Relation to Working in a Confined Space – Part 1

Occupational Health & Safety Requirements in Relation to Working in a Confined Space – Part 1


In this article, we shall discuss employer’s occupational health & safety (OH&S) obligations in relation to having their employees working in confined spaces. This topic is quite detailed hence it is necessary to split it into 2 articles. In this first installment we shall discuss several matters including defining what constitutes a “confined space” and a “hazardous atmosphere”; we shall also begin our examination of various health & safety compliance requirements which apply to employers who have staff working in this type of environment.


Ministerial Regulation on the Prescribing of Standards for the Administration & Management of Occupational Safety, Health And Work Environment in Confined Space B.E. 2547 (2004)

This Regulation sets out a number of standards and obligations which employers must comply with in relation to their staff working in a confined spaces, we shall address several of these below.


What is the legal definition of a “Confined Space”?

To begin with it is necessary to define what constitutes a “confined space”, according to clause 2 of this Regulation it is defined as meaning: “a place which has limited area for entrance and exit with insufficient ventilation that is unable to produce hygienic and safe conditions, e.g., in a tunnel, cave, well, pit, underground room, safe room, fuel tank, fermentation tank, tank, silo, pipe, furnace, container or other objects of similar characteristics.”



Compliance Requirements on Employers:


1.       Warning Signs

Employers are required to affix a signboard of a conspicuous size at the entrance and exit of every confined space. The text on such sign must read “Confined space, Danger, Do not Enter”. If an employer has staff from various nationalities who are unfamiliar with Thai language, then the writer recommends that the text on the warning signs should also be in languages familiar to the international staff so that they can understand the risk as well.


2.       Limiting Access to Confined Spaces

Employers must not allow an employee or any other person to enter a confined space in their workplace unless the employer has provided the necessary safety precautions as provided under this Ministerial Regulation. Furthermore, such employee or person must have been granted permission to enter the confined space by the person who is responsible for granting permission in the workplace who must be trained in accordance with the requirements provided under this Regulation. Details on who can grant permission as well as their training requirements will be discussed in our next article.

Employers should also be aware that they are required to block access to confined spaces for employees or persons who suffer from respiratory disease, heart disease or other diseases considered by a physician that may be harmful to such person if they enter the confined space.


3.       Assessing Conditions in Confined Space to Determine if Hazardous Atmosphere is present

Employers are legally compelled to conduct and record measurements in confined spaces in the workplace including an assessment of the air condition in order to determine if a “hazardous atmosphere” exists. Such checks and measurements must be conducted before an employee is allowed to enter the confined space and during their work in this area. It is worth noting that according to the Ministerial Regulation, “hazardous atmosphere” is defined as meaning “air conditions in which an employee may be exposed to danger due to one or more of the following conditions:

(1)    Existence of oxygen at a concentration lower than 19.5 percent or in excess of 23.5 percent by volume;

(2)    Existence of flammable or explosive gas, vapor, or mist at a concentration in excess of 10 percent of its lower flammable limit or lower explosive limit in the air;

(3)    Existence of flammable or explosive dust at a concentration equal to or in excess of its lower flammable limit or lower explosive limit in the air;

(4)    Existence of any chemicals at a concentration in excess of the standard prescribed by the Ministerial Regulation on the Prescription of Standard for Administration and Management of Occupational Safety, Health and Environment in relation to Hazardous Chemicals; and

(5)    Any other conditions which may be harmful to physical health or life as prescribed by the Minister of Labour.


4.       Obligations on Employers if a Hazardous Atmosphere is Detected

If a hazardous atmosphere is detected by the employer when it conducts measurements then it is required to comply with the following steps:

  1. Remove the employees and other persons in the confined space from such area immediately;
  2. Assess and find out the cause(s) of the hazardous atmosphere;
  3. Remedy the air condition in the confined space to ensure that it is free from the hazardous atmosphere, this can be achieved through such as measures as air ventilation.

If the employer has taken the above actions (A-C) and the hazardous atmosphere still remains in such confined space but the employer is required to allow an employee or any other person to enter the confined space having such hazardous atmosphere, then the employer must arrange for the employees or such other person to wear or use personal protective equipment to enable the said persons to safely work in that confined space.

It is also worth noting that the employer is required to keep detailed records of the results of measurement it takes regarding the assessment of the air condition as well as any remedial actions it carries out to make the air condition in a confined space free from such hazardous atmosphere. Such records must be available for inspection by labour inspectors.


In Part 2 of this article we shall continue examining and discussing the various occupational health & safety compliance requirements on employers who have staff working in confined spaces. Should you require any legal support relating to workplace health & safety laws then please contact us at Dharmniti Law Office Co., Ltd. 2/2 Bhakdi Building 2nd Floor, Witthayu Road, Lumphini, Pathumwan, Bangkok 10330  Tel: (66) 2680 9777 Fax: (66) 2680 9711 Email: ryan@dlo.co.th or info@dlo.co.th


Writer: Ryan Crowley- Foreign Services Manager