A system to vent away anesthesia gases in pediatric operating rooms run by KidsOR or others
Author: Lawrence Kincheloe
Target Organization: Public Invention (in collaboration with Robert Read & Dave Tipping)
Status: Draft Concept Proposal
License: Creative Commons Attribution 4.0 International (CC-BY-4.0) / MIT (Open Source)
In clinical, veterinary, or research environments, waste anesthetic gases (WAGs)—primarily halogenated ethers like isoflurane, sevoflurane, and desflurane—must be captured and neutralized to prevent environmental release and occupational health hazards. The current standard practice utilized by Dave Tipping and others involves passing waste air streams through a chemical absorber bed, typically loaded with Sodium Hydroxide ( / pure lye). While is cheap, universally accessible, and chemically effective, it acts as a consumable reactant rather than a catalyst. As it binds to the fluorine/chlorine atoms to form mineral salts, it becomes saturated.
There is no automatic indicator or notification when the bed is saturated (spent), leading to gas breakthrough.
There are no active, low-cost sensors in the workspace to alert personnel if anesthetic gas leaks or escapes into the room.
Transitioning to a heated or UV-activated solid-state catalytic system (such as or Zeolites) eliminates the need for raw , but still generates corrosive hydrogen fluoride () gas, requiring its own sacrificial lime or water-scrubbing consumables.
Instead of simply replacing one complex consumable system with another, this project proposes a dual-track approach focusing on smart monitoring (highly accessible IoT sensors) and optimized, smart chemical absorption.
Rather than redesigning the chemical scrubbing process entirely, we can significantly increase safety by designing a low-cost, open-source ambient gas detector.
The Concept: A wall-mounted or desktop sensor unit that continuously measures volatile organic compounds (VOCs) and isolates the specific parts-per-million (ppm) threshold of anesthetic gases.
Hardware Integration: The unit can leverage existing open-source IoT sensor architectures, such as the Krake platform, using a microcontroller (e.g., ESP32) paired with sensitive metal-oxide semiconductor (MOS) gas sensors or photoionization detectors (PID).
Alert Mechanism: If room levels of the gas exceed safe occupational exposure limits, the device triggers visual/audio alarms and sends remote alerts via IoT protocols (Wi-Fi, MQTT).
To keep the system highly accessible and low-cost, we can continue using widely available lye () but solve the "exhaustion blind spot" by inventing an inline exhaustion sensor.
pH-Based Optical Sensing: As neutralizes during halogen capture, its pH drops from highly basic () toward neutral. By integrating a simple colorimetric pH indicator (e.g., phenolphthalein embedded in a transparent viewing window) or an inline electronic pH/conductivity probe, the system can automatically flag when the chemical bed is depleted.
Byproduct Trap Alert: Integrating a simple, cheap color-change warning directly on the canister ensures operators know exactly when to swap or recharge the lye bed without relying on guesswork.
Alert Mechanism: A simple white led and color sensor along with a pH sensor could alert when the the solution is sufficiently saturated to warrant replacement. The device triggers visual/audio alarms and sends remote alerts via IoT protocols (Wi-Fi, MQTT).
For field or low-resource settings, design an optimized, modular blueprint for a 3D-printable or DIY-constructible scrubbing canister that utilizes locally sourced materials (like grocery-store lye/wood ash) and features the aforementioned smart-sensing integrations. This could be added in addition to the existing system as a second stage open source emergency backup, while also acting as a modular extension without replacing existing hardware solutions.
To successfully transition this from a one-pager to an active Public Invention repository, we require support in the following domains:
An expert to verify the cross-sensitivity of off-the-shelf VOC sensors (such as the BME680 or specialized electrochemical sensors) to halogenated ethers like isoflurane and sevoflurane, establishing calibration parameters.
To help write the microcontroller logic for reading the sensor output, mapping it to PPM equivalents, and triggering the notification stack. Mechanical/Industrial Design: To model a 3D-printable chamber housing the medium alongside a transparent viewing port for colorimetric pH indicators or electronic sensor insertion.
Conduct a literature search or simple test bench setup to determine which low-cost electronic sensors reliably react to trace anesthetic gases.
It seems that halogenated ethers are generally detectable by VOC sensors, if the UV lamp has sufficient energy to ionize them https://pmc.ncbi.nlm.nih.gov/articles/PMC12115474/.