SCBA vs Escape Pack for H2S: Which One You Need and When

An escape pack gets you out; an SCBA lets you go in. Hydrogen sulfide at 100 ppm or more is immediately dangerous to life and health (IDLH), and OSHA only allows two respirators for working in an IDLH atmosphere: a full-facepiece, pressure-demand SCBA rated for at least 30 minutes, or a pressure-demand supplied-air respirator (SAR) with its own auxiliary air bottle (OSHA H2S fact sheet; 29 CFR 1910.134). An escape pack, often a 5-, 10- or 15-minute hood or bottle, is certified only for getting out, and operator rules like the Devon Energy H2S protocol say it's never to be used for rescue or for work.

What each one is for

The OSHA rules behind the table are in 29 CFR 1910.134, paragraph (d)(2). Durations in the middle and right columns come from the Devon Energy H2S protocol; your operator's sour gas plan may set its own.

When you need an SCBA

Use an SCBA, or SAR with an escape bottle, any time the H2S level is at or above 100 ppm or isn't known. OSHA says that when the employer can't identify or reasonably estimate the exposure, the atmosphere must be treated as IDLH, so a tank top, a vessel, a confined space or a leak you haven't gauged gets the same protection as a confirmed 100 ppm (29 CFR 1910.134). Below 100 ppm, the OSHA H2S fact sheet says an air-purifying respirator with the right cartridge may be used, but your operator's H2S plan may require supplied air at a lower level, so follow the stricter rule. For what different readings mean for your body, see what level of H2S is dangerous.

SCBA work in IDLH air also comes with a team rule. 29 CFR 1910.134 requires at least one standby person outside the area who keeps in touch with the people inside, is trained and equipped for rescue, and has a pressure-demand SCBA or SAR with an auxiliary SCBA plus retrieval gear where it applies. The employer or its designee has to be notified before that standby person goes in. In practice, nobody goes into H2S alone, and the person who goes in after a downed worker wears a full SCBA, not the escape pack off their belt.

When an escape pack is the right tool

An escape pack is for the moment your H2S monitor alarms or a release happens and you're not already on supplied air. You put it on and walk out, upwind or crosswind, to the safe briefing area. 29 CFR 1910.134 requires escape-only respirators to be NIOSH-certified for escape from the atmosphere they'll be used in, so make sure yours is rated for H2S.

The 5, 10 or 15 minutes on the label is a rating, not a promise. Breathing hard while you hurry uses air faster, so the Devon Energy H2S protocol says escape packs must never be used for rescue. Rescuing someone without an SCBA is how one H2S victim becomes two.

Supplied air on sour sites

On a well with high H2S, crews often work on a SAR line fed from a cascade trailer instead of carrying a full SCBA all day. OSHA only accepts that for IDLH work when the SAR facepiece is pressure-demand and includes an auxiliary self-contained air supply, so the worker can get out if the hose is cut or the cascade fails (29 CFR 1910.134). The Devon Energy H2S protocol sets that escape bottle at a minimum of 5 minutes and requires SCBA cylinders of at least 30 minutes.

Inspection, charging and records

An SCBA that's half empty or past its inspection can fail when it's needed most. Here's what 29 CFR 1910.134 paragraph (h)(3) requires:

• Emergency respirators, including SCBAs staged for emergencies, are inspected at least monthly and checked before and after each use.
• Escape-only respirators are inspected before they're carried into the workplace.
• SCBA cylinders are kept fully charged and recharged when they fall to 90% of the manufacturer's recommended pressure. The regulator and low-air warning device must work.
• Emergency respirator records show the date, the inspector, what was found, what was fixed, and the serial number, on a tag at the storage compartment, with the respirator, or in inspection reports.

Medical clearance, fit testing and facial hair

Before anyone wears a tight-fitting respirator, 29 CFR 1910.134 requires three things:

1. A medical evaluation, done before the fit test or first use.
2. A fit test before first use, whenever a different facepiece is used, and at least once a year after that.
3. A clean seal. OSHA doesn't allow tight-fitting facepieces on anyone with facial hair that comes between the seal and the face. Beards and wide sideburns are a common reason someone can't be cleared for SCBA work.

Everyone on site should also know how to put on both pieces of gear quickly. Classes like H2S Awareness and H2S Clear include donning practice, and our H2S training in Midland page covers class options and renewal.