The Department of Defense (DOD) is seeking innovative solutions for a regenerable CO2 scrubbing system to enhance the performance of self-contained breathing apparatuses (SCBAs). The objective is to develop a continuously regenerable system that significantly reduces the weight and heat generation associated with current CO2 removal methods, thereby extending the operational lifetime of SCBAs used in hazardous environments. This technology is crucial for military operations that require prolonged use in immediately dangerous to life and health (IDLH) atmospheres or unknown CBRN environments. Interested parties should note that the solicitation is set to open on January 29, 2025, with applications due by February 26, 2025, and can find more information at the DOD SBIR website.

## Description

A SCBA is a type of respiratory protection device that provides breathing gas from a source independent of the surrounding atmosphere. A closed-circuit SCBA or &ldquo;rebreather&rdquo; re-circulates the breathing air after the carbon dioxide has been removed and the oxygen content restored. Carbon dioxide is typically removed using an absorbent material such as soda lime that cannot be regenerated and must be replaced when expended. Additionally, this carbon dioxide removal process uses an exothermic reaction where the generated heat must be removed using ice or re-freezable cooler packs,1 thus increasing the weight and logistics.A novel approach is needed to overcome the weight and heat generation associated with carbon dioxide removal. Recently, an explosion of research on carbon capture technology has led to the discovery of new sorbent materials to remove low levels of CO2 while operating in humid environments.2,3 As the scale of environmental carbon capture is so large, the only cost-effective sorbents must be easily regenerable. To extend the lifetime of a SCBA CO2 scrubber, the use of these types of sorbents would require a system capable of sorbent regeneration while in operation. One potential solution for this would be a miniature vacuum-swing adsorption system. Any system will still be required to meet size, weight, and heat generation requirements. Technologies that are non-hazardous in use and disposal are desirable. Ultimately, the goal is to develop a longer lasting, lower profile, and lighter weight SCBA for unique military operations. Such operations may include prolonged entry into immediately dangerous to life and health (IDLH) atmospheres or unknown CBRN environments.

## Objective

To develop a continuously regenerable CO2 scrubbing system to extend the operating lifetime of a self-contained breathing apparatus (SCBA) while maintaining size and weight limits needed for reduced logistical burden.

## Phase I

Develop a regenerable, high humidity, low-pressure carbon dioxide removal system that offers significant improvements in the weight and heat generation associated with currently used absorbent materials and ice packs. Determine potential sorbents for relevant SCBA environments. Demonstrate feasibility of proposed enabling technology through computer models based on existing data. Identify key performance parameters and test criteria relevant to closed-circuit SCBA applications. Establish test set up and procedures to assess and validate proposed approach. Fabricate physical &ldquo;breadboard&rdquo; model and conduct bench top testing to characterize the performance of the proposed solution. Record data related, but not limited to, the following: adsorption capacity, desorption rate, adsorption enthalpy (thermodynamic properties), power requirements, and efficiency under relevant temperature/humidity conditions.

## Phase II

Refine and optimize Phase I breadboard model to improve carbon dioxide removal capacity and performance. Perform follow-on bench top evaluations to verify improvements made to the basic enabling technology. Modify test setup and improve test procedures as required. Develop functional scalable prototype by incorporating enabling technology into a suitable test bed (e.g., carbon dioxide storage platform or container). Characterize test bed performance under an operational relevant range of external environmental (temperature/humidity) conditions and in-mask heat/humidity loads. The evaluations should include characterizing the breathing air quality, release of any by-products, exothermic reactions, and other factors relevant to the technology. Based on results obtained, implement necessary refinements to the scalable test bed model.

## Phase III: Dual Use Applications

PHASE III: Fully integrate solution into a full-scale, fully-functional prototype containment unit comparable to the size and weight of a typical re-breather carbon dioxide absorbent and cooling mechanism. Demonstrate ability of the technology to be incorporated into a fully-functional closed-circuit SCBA through modification of an existing off-the-shelf system. Expand applications to other commercial markets to include industrial and homeland defense closed-circuit SCBAs. PHASE III DUAL USE APPLICATIONS: Potential alternative applications include firefighting, industrial, mine rescue, and escape SCBAs. Other possible applications include gas purification, gas separation, and underwater breathing devices (scuba).

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