Grantee Research Project Results
Final Report: Inexpensive Formaldehyde Sensors for Indoor Air Quality (IAQ) Applications
EPA Contract Number: 68HERD19C0004Title: Inexpensive Formaldehyde Sensors for Indoor Air Quality (IAQ) Applications
Investigators: Weber, Andrew
Small Business: Giner Inc.
EPA Contact: Richards, April
Phase: II
Project Period: December 1, 2018 through November 30, 2020 (Extended to November 30, 2021)
RFA: Small Business Innovation Research (SBIR) - Phase II (2018) Recipients Lists
Research Category: SBIR - Air and Climate , Small Business Innovation Research (SBIR)
Description:
Formaldehyde (HCHO) is a well-known harmful volatile organic compound (VOC) responsible for a wide variety of respiratory and dermatological ailments often as a result of chronic exposure. Although formaldehyde is naturally produced, human activity is predominately responsible for its presence in indoor environments. Emission sources of indoor formaldehyde include composite wood products, building materials and insulation, and numerous other consumer products. Formaldehyde is also emitted into the environment as a direct byproduct of unvented, fuel burning appliances, like gas stoves or kerosene space heaters and cigarette smoke.1 Based on growing concerns regarding indoor air quality, there is an increasing interest in devices to accurately measure indoor formaldehyde concentrations. However, despite the associated health hazards and increasingly ubiquitous presence of formaldehyde no user-friendly option exists. A simple to use, low-cost formaldehyde monitoring platform would improve availability to effected persons, help gauge when engineering controls (including on-demand mechanical ventilation) are required, and assess their effectiveness in minimizing indoor exposure.
To address these interests, the Phase II program designed, fabricated, and tested an inexpensive electrochemical formaldehyde monitor that consists of a sensor module and a hand-held analyzer. The sensor module is connected to the hand-held analyzer that can control, process, and transmit (through Bluetooth) the sensor's response signal to a nearby smart device or computer, Figure 1. Giner's sensor technology integrates a solid-polymer-electrolyte and thick film electrodes for quantitative detection of formaldehyde. Using chronoamperometry the sensor generates a current proportional to the formaldehyde gas molecules oxidized at the surface.
Along with advances in limit of detection down to 50 ppb, detection range up to 2000 ppb, high stability (<1% current drift over 24 hours), and long lifespan (>3-months), the Phase II program has also developed an alpha prototype for automated and continuous monitoring of formaldehyde. The components were constructed using 3D printing and custom printed circuit board (PCB) electronics. With on-board power it is capable of formaldehyde detection in an ambient environment for 24 hours before charging. Data is transmitted through Bluetooth to a nearby smart device or computer
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Figure 1. Giner's ambient formaldehyde monitor developed during Phase II.
Summary/Accomplishments (Outputs/Outcomes):
During this Phase II period Giner successfully developed a sensor and prototype that features:
- 50-2000 ppb HCHO detection with 50 ppb resolution when directly in-line of a formaldehyde source or 125-2000 ppb HCHO detection in ambient environments
- Interchangeable sensor module with a lifespan of >3-months and <$20 in materials cost
- Hand-held alpha prototype HCHO analyzer with 24-hours on-board power before requiring charge and <1% signal drift over that time period
- Bluetooth data communication to a nearby smart device or computer
- 3D printed parts and low-cost electronics with a total materials cost of <$60
Conclusions:
During the Phase II program, Giner has developed a low-cost alpha prototype analyzer with a sensor capable of detecting formaldehyde down to 50 ppb direct or 125 ppb ambient, well below the current OSHA permissible exposure limit (PEL) of 750 ppb and the NIOSH recommended exposure limit (REL) of 160 ppb. Furthermore, the platform's wireless data reporting, low maintenance requirements, and automated operation make a user-friendly device to monitor indoor ambient air quality. When compared with other commercially available formaldehyde detectors, this simple, low-cost approach offers the first analyzer suitable for wide public adoption.
The thick film sensor has been characterized in environments of varying temperature (15 - 35 C), humidity (10 -75% relative humidity), and interfering species (carbon monoxide, carbon dioxide, nitrogen dioxide, Clorox® , Windex®, methane, ethane, ethylene, and ethanol). While Giner did a thorough analysis of environmental factors' effects on individual sensor response, the Phase II prototype would also need to be subjected to similar testing at expanded temperature and humidity ranges as well as in the presence of additional VOC containing products often found in the home.
Giner has developed an alpha prototype analyzer to continuously monitor low formaldehyde concentrations for indoor environments. The instrument contains Bluetooth for remote control and data transmission to any nearby computer or smart device. It runs off a single rechargeable lithium ion battery but can use standard residential and commercial wall outlets as well. Based on component costs, the system hardware will have a retail price of $100, with replacement sensors (which can be easily swapped in and out) expected to be available for $50. Sensor lifespan has been tested to 3-months, however, this was due to program time constraints and actual operational longevity is likely much longer.
The linear response range of the sensor is 0-2000 ppb formaldehyde, and sensor performance is not impacted by temperature (15-35 °C) or humidity (10-75% RH). The technology is capable of HCHO monitoring, at OSHA, EPA, and WHO relevant concentrations, within a wide environmental window.
Our system will represent the most affordable option available by far and at the time of this publication is one of only three models offering wireless communications. The other two options with this capability cost $720 (RAE Systems ToxiRAE Pro) and $3,720 (PPM Technology htV-M). Additionally, many of the available formaldehyde analyzers have issues with drift and frequently require calibration before use. Two low-cost commercial devices were used during Phase II to compare with our own prototype analyzer. The Extech VFM200 HCHO Meter ($340) and Aigik Formaldehyde Air Quality Monitor ($99) both experienced significant response drift (±250-500 ppb HCHO) as well as problems with specificity. The environmental presence of alcohols, acetone, and other VOCs often resulted in generating a response from these two commercial analyzers and even triggered their respective alarms despite the lack of formaldehyde in the environment.
In summary, while there are a number of portable and continuous formaldehyde sensors in the market, these miniaturized sensors experience signal drift, are inaccurate, are significantly more expensive than Giner's solution, and fall short on meeting the need to detect HCHO at the lower end of expected indoor levels. Giner's solution bridges this gap by providing a cost-effective continuous sensor module with ppb level detection to enable early warning of HCHO accumulation and avoid chronic exposure.
SBIR Phase I:
Inexpensive Formaldehyde Sensor for Indoor Air Quality Application | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.