# How a Fuel Cell Humidifier Safely Mixes Exhaust Gases > Hyundai's patent describes a fuel cell humidifier that not only adds moisture to incoming air but also intelligently mixes exhaust gases, including hydrogen, with fresh air using a special valve to make the exhaust safer before it leaves the system. - **Patent:** US 20200266464 - **Original title:** Humidifier for fuel cell - **Owner:** Hyundai Motor - **Status:** Active - **Times cited:** 6 - **Field:** automotive, energy, telecommunications ## What it does This humidifier prepares air for a fuel cell by passing "supply air" through a "humidifying membrane" (Claim 1), which adds moisture. The humidified air then goes to the fuel cell's cathode. Crucially, the system includes a "first valve" (Claim 1) that can selectively connect the fresh air path with the exhaust gas path. This valve opens automatically when the "internal pressure of the second region" (Claim 2), where exhaust gas flows, reaches a certain level. When open, fresh "supply air" mixes with the "exhaust gas" (Claim 1) from the fuel cell, including "exhaust hydrogen" (Claim 2). This mixing reduces the "hydrogen concentration" (Claim 2) in the gas discharged to the exhaust system, enhancing safety. For example, if a fuel cell vehicle produces hydrogen-rich exhaust, this system can dilute it with fresh air before release. ## What it does NOT cover - Humidifiers that do not include a valve for selective communication between the supply air region and the exhaust gas region (Claim 1). - Systems where the valve does not open due to the internal pressure of the exhaust gas region (Claim 2). - Humidifiers that do not mix supply air with exhaust gas to specifically reduce hydrogen concentration (Claim 2). - Humidifiers lacking a separate, pressure-operated valve for exhaust hydrogen introduced from the fuel cell anode (Claim 10). - Humidifiers where the first valve is not installed between the first cap and the exhaust gas outlet (Claim 3). ## The clever bit The core innovation is the "first valve" (Claim 1) that provides selective communication between the fresh air supply and the exhaust gas path. This valve is designed to open automatically based on exhaust gas pressure (Claim 2), enabling the system to actively mix fresh air with exhaust to reduce hazardous hydrogen concentrations before discharge. ## Real-world examples 1. Hyundai NEXO fuel cell electric vehicle 2. Toyota Mirai fuel cell electric vehicle 3. Stationary fuel cell power generators 4. Hydrogen-powered buses ## Why it matters Fuel cells require humidified air to operate efficiently and prevent their internal membranes from drying out. Beyond efficiency, managing exhaust gases, particularly hydrogen, is vital for safety in fuel cell applications like vehicles. This patent addresses both the performance need for humidification and the critical safety requirement of diluting potentially flammable hydrogen in the exhaust stream. ## Frequently asked questions ### What does How a Fuel Cell Humidifier Safely Mixes Exhaust Gases cover? Hyundai's patent describes a fuel cell humidifier that not only adds moisture to incoming air but also intelligently mixes exhaust gases, including hydrogen, with fresh air using a special valve to make the exhaust safer before it leaves the system. ### Who owns patent US 20200266464? This patent is owned by Hyundai Motor. ### When does this patent expire? This patent is expected to expire on September 13, 2039, when the invention enters the public domain. ### What is patent US 20200266464 cited by? This patent has been cited by 6 later patents that build on its ideas. ### What problem does this patent solve? Fuel cells require humidified air to operate efficiently and prevent their internal membranes from drying out. Beyond efficiency, managing exhaust gases, particularly hydrogen, is vital for safety in fuel cell applications like vehicles. This patent addresses both the performance need for humidification and the critical safety requirement of diluting potentially flammable hydrogen in the exhaust stream. ### What does this patent NOT cover? Humidifiers that do not include a valve for selective communication between the supply air region and the exhaust gas region (Claim 1). **Full plain-English explainer:** https://patentbrief.org/patent/us/20200266464/humidifier-for-fuel-cell-20200266464 **Original patent:** https://patents.google.com/patent/US20200266464 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How a Fuel Cell Humidifier Controls Air Moisture with a Smart Valve](https://patentbrief.org/patent/us/10950878/humidifier-for-a-fuel-cell) — This patent describes a fuel cell humidifier that uses two humidifying spaces and a controllable valve to precisely adjust the moisture content of incoming air before it reaches the fuel cell stack, improving efficiency and durability. - [How a Fuel Cell Humidifier Adjusts Air Moisture with a Bypass](https://patentbrief.org/patent/us/11646431/humidifier-for-fuel-cell) — This patent describes a fuel cell humidifier that uses a special bypass path to precisely control how much moisture is added to dry air, improving fuel cell performance. - [How to Prepare a Fuel Cell for Faster, Cheaper Startup](https://patentbrief.org/patent/us/20140045086/pre-activation-method-for-fuel-cell-stack) — This patent describes a method for 'pre-activating' a fuel cell stack by injecting humidified hydrogen, sealing it, and storing it, which helps reduce the time and hydrogen needed for its first full operation. - [How Fuel Cells Reuse Exhaust Hydrogen for High Efficiency](https://patentbrief.org/patent/us/7833668/fuel-cell-system-with-greater-than-95-fuel-utilization) — This patent describes a fuel cell system that captures and recycles over 95% of the unused hydrogen from its exhaust stream using a special pump, significantly boosting efficiency. - [Boosting Fuel Cell Power for Vehicles Using Oxygen Injection](https://patentbrief.org/patent/us/5346778/electrochemical-load-management-system-for-transportation-applications) — A system that boosts a vehicle's fuel cell power by injecting pure oxygen into the air supply when the engine needs extra energy.