Initial Entry Testing >> Warning Signs and Labels

If atmospheric testing indicates hazards in a space, this information must be attached at the point of entry (for example, or ). [29 CFR 1915.11(b)] Some employers, however, require all spaces to be labeled. Warning signs and labels may include a sign, placard, or other form of written communication or pictographs, which can be perceived and understood by all workers. These include:

Figure 1: Sign labeled Safe for Hot Work

"Safe for Hot Work" denotes a space that meets all of the following criteria:

  1. The oxygen content of the atmosphere does not exceed 22 percent by volume;

  2. The concentration of flammable vapors in the atmosphere is less than 10 percent of the lower explosive limit;

  3. The residues or materials in the space are not capable of producing a higher concentration than permitted in paragraph no. 1 or 2 above, under existing atmospheric conditions in the presence of hot work, and while maintained as directed by the Marine Chemist (CMC) or competent person; and

  4. All adjacent spaces have been cleaned, inerted, or treated sufficiently to prevent the spread of fire.

Figure 2: Sign labeled Safe for Worker

"Safe for Workers" denotes a space that meets the following criteria:

  1. The oxygen content of the atmosphere is at least 19.5 percent and below 22 percent by volume;

  2. The concentration of flammable vapors is below 10 percent of the lower explosive limit (LEL);

  3. Any toxic materials in the atmosphere associated with cargo, fuel, tank coatings, or inerting media are within permissible concentrations at the time of the inspection; and

  4. Any residues or materials associated with the work authorized by the Marine Chemist (CMC), Certified Industrial Hygienist (CIH), or competent person will not produce uncontrolled release of toxic materials under existing atmospheric conditions while maintained as directed.

Figure 3: Sign labeled Not Safe for Workers

"Not Safe for Workers" denotes a space an employee may not enter because the conditions do not meet the criteria for "Safe for Workers."

Figure 4: Sign labeled Not Safe for Hot Work

"Not Safe for Hot Work" denotes a space where hot work may not be performed because the conditions do not meet the criteria for "Safe for Hot Work."

Figure 5: Sign labeled Enter with Restrictions

"Enter with Restrictions" denotes a space where entry for work is permitted only if engineering controls, personal protective equipment, clothing, and time limitations are as specified by the Marine Chemist, Certified Industrial Hygienist, or shipyard competent person.

  • Obey signs at all times. Employees should address any questions or concerns about signs to their supervisor or safety department representative.