>Argus Group Application Notes

Using Ventilation to meet Regulatory Requirements for Confined Space Entry

The potential for Hazardous Atmospheres which might result from conditions existing in or around confined spaces or from work tasks conducted within those spaces are of great concern to employers and employees needing access to confined spaces. Ventilation systems commonly applied during entry preparation are intended to dilute contaminated air with uncontaminated air for the purpose of controlling potential airborne health hazards, fire and explosive conditions, odors, and nuisance type contaminants (vapors, gases and particulate). The purpose of this application note is to discuss the regulatory requirements and OSHA field inspection guidelines for Confined Space Ventilation.

Regulatory Requirements

Several regulatory standards address the requirements for ventilation related to entering confined spaces. OSHA’s Telecommunications Standard has provisions that apply to the guarding of manholes and street openings, and to the ventilation and testing for gas in manholes and un-vented vaults, where telecommunications field work is performed on or near underground lines. When unsafe conditions are detected by testing or other means, the work area shall be ventilated and otherwise made safe before entry [1910.268 (o) (B)]. An adequate continuous supply of air shall be provided while work is performed in manholes under any of the following conditions:

1. Where combustible or explosive gas vapors have been initially detected and subsequently reduced to a safe level by ventilation,
2. Where organic solvents are used in the work procedure,
3. Where open flame torches are used in the work procedure,
4. Where the manhole is located in that portion of a public right of way open to vehicular traffic and/or exposed to a seepage of gas or gases, or
5. Where toxic gas or oxygen deficiency is found.

OSHA’s Electric Power Generation, Transmission, and Distribution standard incorporates "Specific ventilation requirements." If continuous forced air ventilation is used, it shall begin before entry is made and shall be maintained long enough to ensure that a safe atmosphere exists before employees are allowed to enter the work area. The forced air ventilation shall be so directed as to ventilate the immediate area where employees are present within the enclosed space and shall continue until all employees leave the enclosed space [1910.269(e)(12)]. The air supply for the continuous forced air ventilation shall be from a clean source and may not increase the hazards in the enclosed space [1910.269(e)(13)].

OSHA’s Welding and Cutting rules for construction also address the ventilation required when welding, cutting, and heating in confined spaces. Either general mechanical or local exhaust ventilation shall be of sufficient capacity and so arranged as to produce the number of air changes necessary to keep the concentration of welding fumes and smoke in the breathing zone within safe limits.[1926.353]

Requirements for ventilation are reiterated under the OSHA’s Subpart P Construction Standard for Excavations [1926.956(a)(3)]. Here it states that work which is to be performed in a manhole or un-vented vault:

1. No entry shall be permitted unless forced ventilation is provided or the atmosphere is found to be safe by testing for oxygen deficiency and the presence of explosive gases or fumes;
2. Where unsafe conditions are detected, by testing or other means, the work area shall be ventilated and otherwise made safe before entry;
3. Provisions shall be made for an adequate continuous supply of air.

OSHA’s most recently promulgated requirements which address the need for ventilation are found in its 1993 General Industry Standard for Permit-Required Confined Spaces [1910.146 (c)(5)(i)]. This standard allows an employer to use alternate procedures for entering a permit space under the conditions set forth in paragraph (c)(5)(i) of this standard. These alternate procedures eliminate the requirements for entry permits, attendants, rescue provisions and mechanical retrieval devices. These alternate procedures require the employer to: demonstrate that the only hazard posed by the permit space is an actual or potential hazardous atmosphere; that continuous forced air ventilation alone is sufficient to maintain that permit space safe for entry; that the employer develops monitoring and inspection data that supports these demonstrations (these documents must be made available to each employee who enters the permit space) and; that if an initial entry of the permit space is necessary to obtain the data the entry is performed in full compliance with the established permit entry requirements. Alternate entry procedures require continuous forced air ventilation shall be used, as follows:

The fundamental principals behind these requirements are clear. When activities require entry into areas whose atmospheres are not well controlled nor adequately characterized, ‘The Solution to Pollution is Dilution’. In combination with effective air monitoring strategies, many of the past incidents resulting in injuries and fatalities could have been prevented by effectively utilizing the benefits of ventilation.

What type of documentation will OSHA look for if an employer uses the alternate entry procedure for Confined Space Entry?

The data must demonstrate that there are no non-atmospheric hazards and that the ventilation will keep the air inside the permit space safe for entry. This should include initial data in the form of:

• Volume of the space to be entered;
• Capacity and configuration of the ventilation equipment to be used;
• Identified atmospheric hazards and potential hazards;
• The sampling results from routine testing of the space from the time ventilating has begun through final determination of acceptable entry conditions;
• Atmospheric hazards created by work in the space.

What is meant by the phrase "immediate area where an employee is or will be present within the space" as used in the Confined Space Entry Standard?

The forced clean air ventilation must be directed to where the employee is working or will be working. If the space is so configured or so large that directed air cannot be delivered by local ventilation (such as fans and blowers), ducting the "clean" air is required.

Note: The exhaust discharge of contaminants from the permit space to areas adjacent to the permit space must not endanger the employees of the other work areas. Also, the supplied air ventilation for the permit space must not cause ventilation imbalances which would create hazards in the work area from which it is taken.

OSHA Criteria for Alternate Entry Procedures

The following criteria were exerpted from the OSHA Instruction CPL 2.100, issued May 5, 1995 by the Directorate of Compliance Programs. The purpose of the document is to provide instruction to inspectors which establishes enforcement policy and provide explanation of the standard to ensure uniform enforcement. These instructions apply to all OSHA Regional Administrators and Area Directors, and they shall ensure that the procedures established by these instructions are followed.

As relevant to the ventilation requirements of 1910.146 General Industry Standard for Confined Space Entry, part (c)(5); OSHA inspectors and their counterparts shall follow the guideline established by evaluating and recording the following:

Are the alternate procedures referenced in paragraph (c)(5) being employed for permit space entry?

Other Considerations

The scope and nature of Confined Space Entry Ventilation requirements require an understanding of ventilation techniques, system design and a thorough evaluation of the hazards present at the job site. For these reasons, those employers and employees responsible for Confined Space Entry programs should seek professional guidance from safety professionals, industrial hygienists, and other knowledgeable personnel to aid in selecting the most appropriate ventilation equipment and design a system that meets applicable safety requirements.

Confined Space Ventilation System with Blower, Duct, Elbow Saddlevent and Universal Mount by Air Systems International.

Air Systems International - 2 Speed Electric Blower with GFI shown with optional blower failure alarm.

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