How to design a mask disinfection device using infrared temperature sensors

    This project is a UV-C/heat, Arduino-controlled face mask disinfection device for Coronavirus (SARS-CoV-2).

    Mask disinfection device

    UV-C/heat, Arduino controlled, face mask disinfection device for Coronavirus (SARS-CoV-2)

    introduce

    FFP1 and FFP2 masks are an essential element of protection during a pandemic. They are intended for single use, but during a crisis, reuse is inevitable and requires a disinfection mechanism (1)⁠. During the ongoing SARS-CoV-2 pandemic, hospitals, medical centers, and research institutions have implemented different disinfection mechanisms for these masks, typically involving ultraviolet germicidal irradiation (UVGI) and/or some form of heat. Despite this, these methods are not suitable for many vulnerable populations, and due to shortages, the reuse of these masks has become the only option. Evidence suggests that SARS-CoV-2 remains highly stable on the surface of surgical masks even after 7 days, further increasing the need for viable mask disinfection methods (2)⁠.

    The project aims to create a low-cost, portable device that can effectively use UVGI and dry heat to sterilize masks from SARS-CoV virions and can be easily replicated by anyone who needs it.

DIY Disinfection Device Making Instructions

    Equipment setup diagram

    The temperature must be maintained within the range of 65+/-5°C

    The lamp must provide UV-C wavelength.

    The disinfection cycle duration is at least 30 minutes. (Recommendation: no longer than 30 minutes to obtain a safer range to avoid potential mask degradation and loss of function.)

    Device size

    First heat test

    Heating system production

    A frying pan with a diameter of 22 cm (induction compatible) with the handle removed.

    Cover the skillet with aluminum foil to reflect UV-C light.

    Make a 20 cm hole in the center of the bottom surface of the box/device.

    To keep the skillet in place, use four metal stands as shown.

    Important: The frying pan should not touch the wood of the box, as it will reduce thermal efficiency. Therefore, it is necessary to choose the appropriate hole diameter and shape the metal bracket according to the following diagram:

    Production of the top cover

    UV-C Systems

    For the UV-C source in this device, an 11W bulb from the "Aquarium Sterilizer" kit was used. The UV-C bulb was taken out and mounted to the top cover at both ends of the bulb as shown in the picture. The bulb was mounted by cutting 4 holes in the top cover and using cable ties/cable ties and soft pads to securely fix the bulb. The top surface was covered with aluminum to reflect the UV radiation.

    Feel free to use other sources of UV-C light. If you don't have access to a crystal tube (used in this project), don't use glass as a substitute because glass blocks UV radiation.

    Making a wire rack to place the mask

    The mask will be placed on top of the wire rack. The wire rack is made using thin copper wires, each wire 30 mm apart. The wire rack is placed 120 mm above the bottom surface. The wire rack is held together by passing the wires through small holes on the front and back surfaces of the box.

    Setting up the Arduino and sensors

    Arduino Overview

    Materials List

    ArduinoUNORev3

    Grove Basic Shield V2,0

    Grove Infrared Temperature Sensor

    Grove Light Sensor (P)

    Button

    Piezoelectric Speaker

    Four Digit Alphanumeric Display - White 0.54" Digits with I2C Backpack

    Wall adapter power supply 12VDC

    Temperature and light sensors:

    Arduino Control

    INIT: In this state, the LED display indicates the temperature, but you have to wait for it to reach the threshold (70°C) before the cycle count starts in the COUNT state

    Count: Minutes from 30 to 0 are shown on the LED display, next to the temperature. In the event of low temperature, or if the UV lamp turns off, the status will change to ERR.

    END: This is the normal state when the elapsed time ends. The speaker will advertise. Press the button again to go to INIT.

    ERR: This is the error state, it will be activated if the temperature is too low or the UV lamp is off. The speaker will advertise. Press the button again to enter INIT.

    alarm

    There are few alarm conditions - if the alarm is on, there will be a specific tone sequence on the speaker and a message will be shown on the LED display.

    Alarm conditions: 1) If the system is in ERR state (UV lamp is off/missing or temperature is too low) 2) If the temperature is too high (over 75°C)

    User Manual

    1. Place the box on top of your induction (or resistance) cooktop.

    2. Turn on the power of Arduino.

    3. Close the box and start heating at 70~80% of the induction cooker power.

    4. Wait until the temperature reaches 60°C. Now reduce the power of the induction cooker to 30%.

    5. Now you can turn on the device, put the mask in and close the device.

    7. Press the button to start => The remaining time should be displayed (30 minutes).

    8. From now on you just have to wait until the time drops to 00 minutes and there will be a signal on the loudspeaker.

    9. To restart a new cycle from the initial state, just press the button.

    Note: When the timer is counting the elapsed time (COUNT state), the small dot between the Timer and Temperature displays will flash at a rhythm of 1 second.

    Temperature Cycle

    Thermal inactivation of viruses

    The ability to remove microorganisms by wet heat, usually at temperatures below 100°C, has been known since Pasteur’s time. In this device, we implemented dry heat, which has been reported to be effective in eliminating the infectivity of SARS-CoV. Analyses have shown that the virus is largely inactivated within 30–90 minutes at 56°C, almost completely inactivated within 20–60 minutes at 65°C, and completely inactivated within 30–45 minutes at 75°C (7, 8)⁠. Furthermore, a recent study showed that SARS-CoV-2 lost all detectable infectivity after incubation at 56°C for 30 minutes or at 70°C for 5 minutes (2)⁠.

    Based on this evidence and additional considerations regarding the impact of these disinfection methods on mask functionality, which are explained in the next section, we decided to set the heat exposure for the protocol used with the device to 65°C for 30 minutes.

    Sterilization protocol on face mask

    So far, we have presented evidence on viral disinfection of samples different from the masks we intend to disinfect. Therefore, we present here some reports on viral disinfection of the same type of masks we intend to use.

    Mask disinfection using UVGI of about 1 J/cm2 (10) ⁠, UVGI of about 18 J/cm2, or moist heat at 65 ± 5 °C for 3 hours is effective against influenza virus (11) ⁠. No studies have been conducted on mask disinfection with coronaviruses, but since influenza virus is also an ssRNA virus, similar effects would be expected.

    in conclusion

    Taking into account the evidence collected and the technical details of the equipment, we decided to set the disinfection protocol to 30 minutes of UVC irradiation and dry heat at 65 ± 5 ° C. This time must be calculated taking into account the time required for the equipment to reach the required temperature and light intensity. Using UVC or heat at these specifications alone should be sufficient to eliminate nearly all SARS-CoV-2 infectivity, and the simultaneous action of both should increase the effectiveness of the method to a safer level.

    Safety considerations

    •UVC radiation is harmful to the skin and eyes. The UVC bulb should only be turned on when the box is closed.

    •Be careful with the metal parts of the box, which may be very hot when heated and may burn your skin.

    Disclaimer

    Based on the available scientific evidence, the disinfection protocol will likely eliminate nearly all SARS-CoV infectivity and will certainly make the masks safer to reuse than without any disinfection. However, Needlab and the members working on this project do not assume any responsibility for the use of this device. It was designed in good faith and to the best of our knowledge and ability, but the following must be stated:

    Appropriate laboratory testing has not been performed on the use of this device to inactivate SARS-CoV-2, and the actual impact on the filtration capacity of the mask cannot be confidently assessed in advance. Use of the device and this guidance is a discretionary decision.

This project is a UV-C/heat, Arduino-controlled face mask disinfection device for Coronavirus (SARS-CoV-2).

Mask disinfection device

UV-C/heat, Arduino controlled, face mask disinfection device for Coronavirus (SARS-CoV-2)

introduce

FFP1 and FFP2 masks are an essential element of protection during a pandemic. They are intended for single use, but during a crisis, reuse is inevitable and requires a disinfection mechanism (1)⁠. During the ongoing SARS-CoV-2 pandemic, hospitals, medical centers, and research institutions have implemented different disinfection mechanisms for these masks, typically involving ultraviolet germicidal irradiation (UVGI) and/or some form of heat. Despite this, these methods are not suitable for many vulnerable populations, and due to shortages, the reuse of these masks has become the only option. Evidence suggests that SARS-CoV-2 remains highly stable on the surface of surgical masks even after 7 days, further increasing the need for viable mask disinfection methods (2)⁠.

The project aims to create a low-cost, portable device that can effectively use UVGI and dry heat to sterilize masks from SARS-CoV virions and can be easily replicated by anyone who needs it.

DIY Disinfection Device Making Instructions

Equipment setup diagram

The temperature must be maintained within the range of 65+/-5°C

The lamp must provide UV-C wavelength.

The disinfection cycle duration is at least 30 minutes. (Recommendation: no longer than 30 minutes to obtain a safer range to avoid potential mask degradation and loss of function.)

Device size

First heat test

Heating system production

A frying pan with a diameter of 22 cm (induction compatible) with the handle removed.

Cover the skillet with aluminum foil to reflect UV-C light.

Make a 20 cm hole in the center of the bottom surface of the box/device.

To keep the skillet in place, use four metal stands as shown.

Important: The frying pan should not touch the wood of the box, as it will reduce thermal efficiency. Therefore, it is necessary to choose the appropriate hole diameter and shape the metal bracket according to the following diagram:

Production of the top cover

UV-C Systems

For the UV-C source in this device, an 11W bulb from the "Aquarium Sterilizer" kit was used. The UV-C bulb was taken out and mounted to the top cover at both ends of the bulb as shown in the picture. The bulb was mounted by cutting 4 holes in the top cover and using cable ties/cable ties and soft pads to securely fix the bulb. The top surface was covered with aluminum to reflect the UV radiation.

Feel free to use other sources of UV-C light. If you don't have access to a crystal tube (used in this project), don't use glass as a substitute because glass blocks UV radiation.

Making a wire rack to place the mask

The mask will be placed on top of the wire rack. The wire rack is made using thin copper wires, each wire 30 mm apart. The wire rack is placed 120 mm above the bottom surface. The wire rack is held together by passing the wires through small holes on the front and back surfaces of the box.

Setting up the Arduino and sensors

Arduino Overview

Materials List

ArduinoUNORev3

Grove Basic Shield V2,0

Grove Infrared Temperature Sensor

Grove Light Sensor (P)

Button

Piezoelectric Speaker

Four Digit Alphanumeric Display - White 0.54" Digits with I2C Backpack

Wall adapter power supply 12VDC

Temperature and light sensors:

Arduino Control

INIT: In this state, the LED display indicates the temperature, but you have to wait for it to reach the threshold (70°C) before the cycle count starts in the COUNT state

Count: Minutes from 30 to 0 are shown on the LED display, next to the temperature. In the event of low temperature, or if the UV lamp turns off, the status will change to ERR.

END: This is the normal state when the elapsed time ends. The speaker will advertise. Press the button again to go to INIT.

ERR: This is the error state, it will be activated if the temperature is too low or the UV lamp is off. The speaker will advertise. Press the button again to enter INIT.

alarm

There are few alarm conditions - if the alarm is on, there will be a specific tone sequence on the speaker and a message will be shown on the LED display.

Alarm conditions: 1) If the system is in ERR state (UV lamp is off/missing or temperature is too low) 2) If the temperature is too high (over 75°C)

User Manual

1. Place the box on top of your induction (or resistance) cooktop.

2. Turn on the power of Arduino.

3. Close the box and start heating at 70~80% of the induction cooker power.

4. Wait until the temperature reaches 60°C. Now reduce the power of the induction cooker to 30%.

5. Now you can turn on the device, put the mask in and close the device.

7. Press the button to start => The remaining time should be displayed (30 minutes).

8. From now on you just have to wait until the time drops to 00 minutes and there will be a signal on the loudspeaker.

9. To restart a new cycle from the initial state, just press the button.

Note: When the timer is counting the elapsed time (COUNT state), the small dot between the Timer and Temperature displays will flash at a rhythm of 1 second.

Temperature Cycle

Thermal inactivation of viruses

The ability to remove microorganisms by wet heat, usually at temperatures below 100°C, has been known since Pasteur’s time. In this device, we implemented dry heat, which has been reported to be effective in eliminating the infectivity of SARS-CoV. Analyses have shown that the virus is largely inactivated within 30–90 minutes at 56°C, almost completely inactivated within 20–60 minutes at 65°C, and completely inactivated within 30–45 minutes at 75°C (7, 8)⁠. Furthermore, a recent study showed that SARS-CoV-2 lost all detectable infectivity after incubation at 56°C for 30 minutes or at 70°C for 5 minutes (2)⁠.

Based on this evidence and additional considerations regarding the impact of these disinfection methods on mask functionality, which are explained in the next section, we decided to set the heat exposure for the protocol used with the device to 65°C for 30 minutes.

Sterilization protocol on face mask

So far, we have presented evidence on viral disinfection of samples different from the masks we intend to disinfect. Therefore, we present here some reports on viral disinfection of the same type of masks we intend to use.

Mask disinfection using UVGI of about 1 J/cm2 (10) ⁠, UVGI of about 18 J/cm2, or moist heat at 65 ± 5 °C for 3 hours is effective against influenza virus (11) ⁠. No studies have been conducted on mask disinfection with coronaviruses, but since influenza virus is also an ssRNA virus, similar effects would be expected.

in conclusion

Taking into account the evidence collected and the technical details of the equipment, we decided to set the disinfection protocol to 30 minutes of UVC irradiation and dry heat at 65 ± 5 ° C. This time must be calculated taking into account the time required for the equipment to reach the required temperature and light intensity. Using UVC or heat at these specifications alone should be sufficient to eliminate nearly all SARS-CoV-2 infectivity, and the simultaneous action of both should increase the effectiveness of the method to a safer level.

Safety considerations

•UVC radiation is harmful to the skin and eyes. The UVC bulb should only be turned on when the box is closed.

•Be careful with the metal parts of the box, which may be very hot when heated and may burn your skin.

Disclaimer

Based on the available scientific evidence, the disinfection protocol will likely eliminate nearly all SARS-CoV infectivity and will certainly make the masks safer to reuse than without any disinfection. However, Needlab and the members working on this project do not assume any responsibility for the use of this device. It was designed in good faith and to the best of our knowledge and ability, but the following must be stated:

Appropriate laboratory testing has not been performed on the use of this device to inactivate SARS-CoV-2, and the actual impact on the filtration capacity of the mask cannot be confidently assessed in advance. Use of the device and this guidance is a discretionary decision.