When American Airlines Flight 729 took off from London’s Heathrow Airport on a routine flight to Philadelphia on Oct. 21, a strong odor engulfed the cabin of the Airbus A330-300, prompting the flight crew to divert to Dublin, where it landed safely. News media reported that passengers complained of burning eyes and itchy skin. Of the 287 customers and 12 crew onboard, two crew members and one customer were taken to the hospital for evaluation, and all were released the same day.
The source of the fumes was a cleaning solution that spilled in the galley.
While fume events are rare, they are a reminder that cabin air has potential health risks. This is because the air supply on nearly all turbine-driven aircraft is a combination of fresh and recirculated air. The fresh air pumped into the cabin is engine bleed air. Currently, the only exception is the Boeing 787, which uses a separate, bleed-free system. Once in the cabin, that air is filtered to screen out pathogens and odors as it is recirculated.
“It is the bleed air that will be contaminated with engine oils, mainly from the compressor bearings compartment, as the oil seals leak—and all engine seals leak,” says Tristan Loraine, cofounder of the London-based Global Cabin Air Quality Executive.
“In recent years, there has been growing concern about the health risks of smoke and fume events from the bleed air, sometimes generated by the failure of an engine oil seal,” he notes.
Loraine还报告说，引气带来的另一种吸入危害是液压油，他指出，液压油约有70％的有机磷酸酯。尽管他补充说HEPA（高效微粒捕集）过滤器已被证明能够非常有效地从再循环空气中去除细菌和病毒，但Loraine指出，关于何时应更换过滤器，仅存在指导原则。他说：“一些航空公司正在安装双HEPA /活性炭过滤器，以从再循环空气中去除[volatile organic compounds (VOC)]挥发性有机化合物（VOC）”
Loraine also reports that another inhalation hazard from bleed air is hydraulic fluid, which, he points out, is about 70% organophosphate. Although he adds that HEPA (high-efficiency particulate arrestance) filters have proven very effective at removing bacteria and viruses from recirculated air, Loraine points out that no regulations—only guidelines—exist as to when they should be replaced. “Some airlines are installing dual HEPA/activated carbon filters to remove [volatile organic compounds (VOC)] from the recirculated air,” he says.
In fact, suppliers of aircraft environmental control systems (ECS) see opportunities in the field of cleaning cabin air and are developing technologies to pursue them.
在去年9月于伦敦举行的国际飞机客舱空气会议上，颇尔航空航天公司（Pall Aerospace Corp.）宣布，其航空航天团队完成了其Purecabin总空气过滤系统的首次全系统地面测试。高级营销总监史蒂夫·辛普森（Steve Simpson）表示，颇尔航空航天公司（Pall Aerospace）的目标是到2020年年中前，将空客A320系列飞机的Purecabin认证为全新风客舱和驾驶舱过滤系统。他补充说，颇尔航空公司预计到2020年年中认证一种传感器，用于检测空气供应中是否存在发动机机油、液压油和除冰液。该传感器将与过滤系统结合或独立工作。辛普森说，Purecabin将首次将经过过滤的引气引入客舱。
At the Aircraft Cabin Air International Conference in London last September, Pall Aerospace Corp. announced that its aerospace team completed the first full-system ground test of its Purecabin Total Air Filtration System. Pall Aerospace aims for certification of Purecabin on the Airbus A320 family by mid-2020 as a full fresh air cabin and cockpit filtration system, according to Steve Simpson, senior marketing director. He adds that by mid-2020, Pall Aerospace expects to certify a sensor that will detect the presence of engine oil, hydraulic and deicing fluid in the air supply. The sensor will work in conjunction with, or independent of, the filtration system. Purecabin, Simpson says, will bring filtered bleed air to the passenger cabin for the first time.
It employs a “high-performance synthetic carbon” which, Simpson explains, has been extensively tested by an independent laboratory against a wide range of chemicals.
“We have demonstrated that this synthetic carbon will mitigate the presence of chemicals that may be found in the cabin air supply, including tricresyl phosphate, or TCP,” he notes. “The Mist and Vapor Eliminators (MaVE) fresh air filters will also remove odors that originate from outside the aircraft or those that are due to system malfunction.”
He says the system has been designed with a minimum-weight, low-maintenance approach. “Weight and maintenance were an important consideration for Purecabin, since it has to be integrated into an existing aircraft system,” he explains.
Simpson confirms that a number of new technologies are under consideration for future filtration. “However, we have to be careful that by solving one problem, we do not create another,” he says. “For example, catalysis can be effective, although in some cases it may produce contaminants of more concern than those currently entering the system.”
Pall Aerospace already has a successful track record with bleed air filtration. The company created a fresh air filter for cockpit retrofit on the Boeing 757-200 freighter—specifically powered by the Rolls-Royce RB211-535—certified by an STC for DHL Aviation. Installed in an existing air duct, the cockpit filter has had full production approval since 2012, under European Union Aviation Safety Agency (EASA) declaration of design performance (DDP) approval. To date, the DHL 757-200 freighters are the system’s only application, although other airlines, which Simpson is not at liberty to disclose, are considering it.
Stacy Morrissey, managing director of fleet engineering for American Airlines, reports that the carrier has been working with filter manufacturers for the past several years on fresh air filtration systems by providing aircraft, facilities and support for full-scale ground tests. However, she cautions that while the technology is promising, retrofits are not expected to be easy or inexpensive.
“As with many projects, there are technical issues that must be overcome. For this project, for example, we need to make sure that airflow to the cabin and the ability of the system to control temperature is not appreciably affected with the filters installed,” says Morrissey.
In the meantime, a new approach to cabin air purification by Savannah-based Aviation Clean Air (ACA) could make it unnecessary to use the more expensive filters in aircraft cabins and cockpits, according to Mallie Seckinger, managing member. ACA was established in 2012 to develop and market its eponymous Aviation Clean Air component, which is available for retrofit under an STC from Southern Aviation Parts and Service (SAPS), ACA’s certification engineering partner and majority shareholder.
As Seckinger explains, Aviation Clean Air’s ACA component is “100% green technology” since it is completely electronic, uses no chemicals and produces no odors or harmful byproducts. “The technology replicates and accelerates nature’s natural cleansing, odor-elimination and pathogen disinfection process through an electronic ionization process,” he says.
Activation commences when the aircraft’s ECS is switched on, and air begins flowing into the cabin and cockpit through the air ducts. Seckinger stresses that the system is not a filter and has no filter-system structural characteristics. “The component is quickly installed seamlessly in the air ducts, has no moving parts to wear out and requires no scheduled maintenance,” he remarks. The system weighs 2 lb., including mounting hardware. The number of components needed per aircraft depends upon the layout of the existing duct system. “As examples, a Gulfstream G550 requires two, while a Boeing 737 requires four,” he says.
The ACA component, Seckinger points out, was designed to achieve continuously improved air quality, along with surface purification, simultaneously. “Within just a few seconds, it proactively and effectively controls both existing as well as newly created odors, such as VOCs, including those associated with, but not limited to, fuel emissions and the fueling process,” he says. “It also eliminates cooking, cleaning and stale air odors, wherever the conditioned ECS air reaches.”
Seckinger says that the ACA component also kills existing as well as newly created pathogens brought into the aircraft and spread by aircraft servicing personnel, passengers or crew members through touching, coughing or sneezing—throughout the cockpit and cabin—significantly reducing the likelihood of flight-acquired diseases.
Initially installed on a Falcon 2000 in 2014 under an FAA Form 337 Return to Service following an alteration or modification, the ACA component is certified on in-production and in-service Gulfstream jets—specifically the G450, GV, G550, G650 and G650ER, either under an STC or Form 337. Also certified on the Leonardo AW169 helicopter, it is now on the verge of a commercial air carrier application for the first time.
塞金格解释说：“ACA组件已经包含在一些客机的VIP配置中，特别是波音737-800、737 BBJ、737 MAX 8、空客A320和A330-200。”“我们认为航空公司市场是一个增长机会，事实上，我们正在与两家航空公司商谈机队改造事宜。”
“The ACA component has been included with some airliner VIP configurations, specifically on the Boeing 737-800, 737 BBJ, 737 MAX 8, Airbus A320 and A330-200,” Seckinger explains. “We see the airline market as a growth opportunity, and, in fact, we are in talks with two airlines about a fleet retrofit.”
While he could not disclose those airlines’ names, he did comment that the focus is on the A320 and 737. Seckinger reports that ACA can either sell the components individually to meet the airline requirements per their drawings for installation, or the vendor can manufacture any required hardware for the installation.
柯林斯航空（Collins Aerospace）飞机客舱空气质量总工程师兰斯•巴托斯（Lance Bartosz）证实，该公司目前在大型商用飞机波音787上提供的仍然是唯一的100%新鲜空气ECS。正如他所解释的，传统的由发动机提供的增压引气被电动机驱动的压缩机所取代，这些压缩机吸收外部环境空气并为机舱提供增压空气。巴托斯说：“这将使发动机排出的空气与机舱空气完全分离，并在各种运行模式下精确地根据飞机的要求调节空气流量，在降低油耗的同时提高机舱舒适度。”。
Lance Bartosz, chief engineer for aircraft cabin air quality at Collins Aerospace, confirms that the company provides what is still the only 100% fresh air ECS on large commercial aircraft—currently the Boeing 787. As he explains, the traditional pressurized bleed air provided by the engine is replaced by electric-motor-driven compressors that take in outside ambient air and provide pressurized air for the cabin. “This completely decouples the engine bleed air from the cabin air and precisely tailors air flow to aircraft requirements throughout all modes of operation, increasing cabin comfort while reducing fuel consumption,” says Bartosz.
With the arrival of more-electric aircraft, Bartosz explains that there is now a tradeoff between traditional pneumatic or a more electric function. “Bleed air usage is considered a fuel penalty since it takes away some energy generated by the engine for a purpose other than propulsion. Depending on the aircraft and ECS configuration, for example, it could be more efficient to generate pressurized air using an electric compressor.”
Collins Aerospace, he says, continues to work with its filtration partners to develop ways to optimize the ECS and improve passenger comfort with air quality, humidity, temperature and fresh air flow rate.
“In some cases, we may consider the addition of new equipment to improve the cabin environment. But adding new components such as additional filters to an existing aircraft can adversely affect the cabin conditions if the system is not properly engineered. While we try to minimize the additional weight and maintenance associated with adding components, inevitably it is unlikely to result in a zero net impact,” he says.