The incorporation of adjacent hazards is an important safety consideration for all confined space entry since hazards adjacent to the space can significantly affect the hazards in the confined space.

Why Use NFPA 350, Guide for Safe Confined Space Entry and Work?

OSHA tells you what to do; NFPA 350 tells you how to do it by providing supporting information on how to identify hazards, perform gas monitoring, control hazards, and ventilate.

The question I am most frequently asked about NFPA 350, Guide for Confined Space Entry and Work is, "Why do we need another confined space standard?" OSHA's Permit Required Confined Space Standard became effective in 1993, finally leading the way to safer confined space entries. OSHA's Confined Spaces in Construction standard, released in 2015, is expected to further improve confined space safety.

While documentation of fatalities in confined spaces has been incomplete, the general consensus is that between 90 and 100 workers die each year in confined spaces. These numbers seem to remain consistent despite regulations. In fact, the most recent Census of Fatal Occupational Injuries published by the Bureau of Labor Statistics showed that 136 workers were killed in incidents associated with confined spaces in 2015. This indicates either an alarming increase in deaths or better reporting.

Those of us who work in the confined space world read about single or multiple confined space fatalities on a weekly basis. Despite regulations, there is clearly still room for improvement. NFPA's Guide for Safe Confined Space Entry and Work supplements OSHA standards and provides additional guidance on "how to" enter and work in confined spaces to improve confined space entry programs.

While some of the confined space fatalities are due to a simple lack of compliance with existing OSHA standards, others appear to result from gaps in existing standards and confusion about what is required for confined space entry. The standards used in confined space entry are performance standards, meaning they focus on the desired outcome—preventing injuries and fatalities in confined spaces. But like most performance-based standards, they often lack sufficient guidance on "how to" reach that desired outcome. NFPA 350 fills the voids and addresses these gaps, minimizes confusion in terminology, and provides practical guidance on how to apply requirements in existing standards to improve confined space safety.

Terminology Simplified
Perhaps one of the most confusing parts of confined space safety is the terminology used by safety professionals and regulators to describe confined spaces. The terms "confined space" and "non-permit confined space" can be used interchangeably to describe a confined space where no hazards are present. However, this same space becomes a "permit-required confined space" the very next day when an employee enters it to weld or paint. The type of space is different from day to day and depending on what is being done inside the space. Furthermore, there are several different procedures that can be used for entering permit-required confined spaces. "Reclassification procedures" are allowed in spaces where all hazards have been eliminated. "Alternate procedures" are allowed where the only hazard is atmospheric and controlled by ventilation. A full permit is needed for entry where other hazards exist. Even confined space professionals have expressed difficulty over how to best explain the differences in requirements for entry to employees and employers.

To minimize confusion, NFPA 350 uses one term—confined space—throughout the document, instead of renaming a space based on the presence or absence of a hazard. All spaces that meet the OSHA definition of a confined space are referred to simply as "confined spaces" in NFPA 350.

The guide also establishes one procedure for all confined spaces, starting with a pre-entry evaluation form. All spaces are evaluated on their own merit based on hazards that are inherent, introduced, or adjacent to the space. Whether a permit is required for entry depends on the hazards or potential hazards identified in the pre-entry evaluation form. This approach of using a checklist to evaluate all spaces prior to issuing a permit is already in practice in some industries.

Inherent, Introduced, and Adjacent Hazards
Both the pre-entry evaluation form and the permit form remind the user to look for hazards that are inherent, introduced, and adjacent to the space. While most confined space entry programs incorporate the evaluation of inherent and introduced hazards, few address adjacent hazards. The incorporation of adjacent hazards is an important safety consideration for all confined space entry since hazards adjacent to the space can significantly affect the hazards in the confined space. There have been many incidents where fatalities were documented or suspected when an employee was exposed to a hazardous atmosphere adjacent to a confined space that caused the employee to fall into a confined space or led to an explosion when welding was done in a space without considering the adjacent space hazards. NFPA 350 takes one additional precaution at this juncture, recommending atmospheric monitoring prior to any confined space entry, even if hazards are not found on the pre-entry evaluation.

The default position to perform atmospheric monitoring prior to entry into any confined space is akin to "assuming the dog will bite until you find out otherwise." Because atmospheric hazards continue to be the source of many confined space fatalities, the few minutes it takes to perform this monitoring is time well spent to verify that the atmosphere is not hazardous.

If no physical or atmospheric hazards are found, the pre-evaluation form is signed and no permit is needed. The pre-entry evaluation form also can be used as the written certification required for entry using reclassifications or alternate procedures required by OSHA's Permit Required Confined Spaces standard. If hazards are identified, then a permit is needed and the procedures required for safe confined space entry apply.

OSHA tells you what to do; NFPA 350 tells you how to do it by providing supporting information on how to identify hazards, perform gas monitoring, control hazards, and ventilate. For example, the atmospheric monitoring chapter explains selection of the appropriate gas monitor, calibration procedures (including zero and bump test), and interpretation of results (including information on interferences and limits of detection). It also includes best practices for gas monitoring, such as shutting down ventilation prior to initial monitoring; testing to determine the amount of time for a sample to travel through a length of tubing and be detected at the sensor; and establishing safe levels for entry. The chapter on ventilation explains how to select and configure ventilation equipment in a confined space depending on the hazard. Information is also provided on ventilation of inert atmospheres and bonding, as well as grounding of flammable or combustible atmospheres. Drawings of typical ventilation configurations are provided in an annex.

Addressing Other Gaps
NFPA 350 also recognizes that demonstrated competencies are critical for those workers involved in confined space entry and work. In addition to the entrant, attendant, and entry supervisor roles defined by OSHA, NFPA 350 provides recommended competencies for those who perform tasks such as gas monitoring, ventilation, and rescue. Those individuals may or may not be the attendant or entry supervisor. For example, the "Gas Tester" as defined in NFPA 350 should be qualified beyond simply knowing how to turn on the gas monitor and record results. This individual also should understand how to calibrate and interpret atmospheric monitoring results. An attendant who is responsible for both monitoring and ventilating a confined space should be qualified as an attendant but also should understand both the gas monitoring equipment and the ventilation method required to maintain safe atmospheric conditions.

Gaps in confined space rescue are also addressed in NFPA 350. The standard outlines the organizational elements of emergency preparedness normally in place in a fire department but not necessarily in a facility rescue program. Providing a tiered approach to response, the rescue chapter also includes information on pre-incident planning and evaluation, rescue gear, rescue configurations, and rescue competencies.

Additional Considerations
Because many confined space incidents relate to change, a chapter on management of change (MOC) has been included in NFPA 350. The MOC system identifies and evaluates potential effects of modifications to confined space configurations, equipment, materials, content, and work tasks. A sample MOC form, provided in an annex, serves to document that the effects of change have been considered.

Finally, NFPA 350 provides a chapter on prevention through design (PtD) specifically for confined spaces. The PtD concept seeks to initiate a design process to reduce or eliminate inherent risks and hazards associated with the design of facilities, equipment, and products. PtD can minimize retrofitting control costs and the use of labor-intensive administrative hazard control measures. PtD targets two types of interactions: the construction and/or installation of new confined spaces; and the redesign, retrofit, and/or renovation of confined spaces to eliminate, control, or minimize hazards. A bibliography of documents related to the design of confined spaces will be updated as the NFPA 350 Technical Committee is made aware of them. For example, there are documents related to manure pit design and ventilation, as well as documents related to the design of water and wastewater facilities that will be listed in the next edition of the standard.

While the implementation of methods provided throughout NFPA 350 will improve confined space safety, the only way to fully prevent confined space incidents is to eliminate the confined space completely through design or redesign.

For More Information on NFPA 350
All NFPA documents are available for viewing free of charge by going to NFPA's website at[document number]. NFPA 350, Guide for Safe Confined Space Entry and Work can be viewed on the document information page at A free downloadable fact sheet and 5 minute video, as well as an online training series and information about on-site training, are also available on this page.

Like all NFPA standards, NFPA 350 is an ever-evolving document that will be revised every three to five years, making the information current and relevant and allowing for public review several times during each revision cycle. To be notified about any activity related to NFPA 350, such as where and when meetings will occur or when the document is open for public input and comment, sign up for e-mail alerts at

This article originally appeared in the August 2017 issue of Occupational Health & Safety.

Product Showcase

  • The MGC Simple Plus

    The MGC Simple Plus

    The MGC Simple Plus is a simple-to-use, portable multi-gas detector that runs continuously for three years without needing to be recharged or routinely calibrated after its initial charge and calibration during manufacturing. The detector reliably tests a worksite’s atmosphere for hydrogen sulfide, carbon monoxide, oxygen and combustible gases (LEL). Additionally, it is durable enough to withstand the harshest treatment and environments, which is why it has an IP 68 rating. The MGC Simple Plus is also compatible with a variety of accessories, such as Gas Clip Technologies’ new GCT External Pump. Visit for more information. 3

  • Magellan X Pte Ltd

    Hesitate No More with SOL-X Connected Worker Health & Safety Solution

    According to the National Safety Council, work-related medically consulted injuries total 4.26 million in 2021 in USA alone. SOL-X solution prevents “human factors” safety issues by anticipating incidents and improving compliance workflows. Leverages digital technologies (IIoT, AI and analytics) to predict patterns from occurring and make informed decisions. Control Of Work - gets rid of tedious paperwork and experience digital workflows. Crew Protect - maximises safety and situational awareness with health trackers and situational indicators. Award-winning Intrinsically Safe SmartWatch – innovative features that enable near real-time visibility and connected well-being. Works well with major connectivity protocols like Wi-Fi, Bluetooth, and Long-Range Bluetooth! 3