To our knowledge, there is no regulatory requirement. However, we’ve heard this before and have used it as well when stressing the importance of proper PPE for rescuers, particularly when IDLH atmospheres may be involved. Here’s our thinking… if the entrant’s PPE did not provide adequate protection and he or she is now requiring rescue assistance, then using their “same level of protection” isn’t going to protect you either!
What triggers the use of a greater level of protection? This comes from the rescuer’s assessment of the hazards – including the use of an independent atmospheric monitor from that used by the entrant(s). That’s why it’s so important for the rescue team to provide their own atmospheric monitoring equipment. It also illustrates why written rescue preplans are so important – you need to preplan what equipment and techniques will be required well in advance of an emergency. It’s critical; the PPE selected must be adequate to protect the rescuers.
When preparing rescue preplans, you must also take into consideration any unusual hazards or circumstances that may arise from any work being done inside or near the space. For example, special cleaning solvents might be used or other hazards may be introduced into the space by the workers. Referencing and understanding the MSDS as well as “listening to what your monitor is telling you” are key factors in PPE determination.
OSHA does mention, however, if the atmospheric condition is unknown, then it should be considered IDLH and the use of positive pressure SCBA/SAR must be used. This will protect you from low O2 levels and other inhalation dangers; however, you must also consider LEL/LFL levels. Other factors include non-atmospheric conditions as well. For example, have you considered “skin absorption” hazards and what precautions must be taken?
So, the bottom line, the decision to go with breathing air for rescuers can be determined from your hazard assessment; or, in some cases, by company policy; and even required by OSHA when there’s an unknown atmosphere involved. Remember, it’s much better to be safe than sorry!