FL420 Pulse Oximeter with Alarm,

$24.95 24.95

FL420 Fingertip Pulse Oximeter (Blue), Blood Oxygen Monitor with Alarm

The FaceLake FL420 Fingertip Pulse Oximeter provides an accurate method for quickly checking pulse rate and blood oxygen saturation (SpO2) levels. The FL420 is able to take a swift measurement reading from any finger. Test blood oxygen levels and pulse rate in under 10 seconds!

The FaceLake FL420 blood oxygen monitor with alarm features a custom threshold monitoring system for alerting the user to measurement readings which are outside of the user’s set limits. When enabled, the pulse oximeter speaker emits a beeping sound if a measurement is detected outside the user’s range setting. Alarm preferences are saved in the device’s memory. 

The large LCD screen clearly displays the user’s body activity information. Taking a reading with this FaceLake pulse oximeter is simple and efficient. The pulse oximeter is clipped onto the user’s finger and operated with a single button. The SpO2/pulse rate sensor takes an accurate measurement of blood oxygen levels and pulse rate within ±2%/±2bpm. 

This compact device can be carried in a pocket, backpack, or other small space. The included lanyard allows the user to wear the device around their neck for use while hiking or training. This device includes two AAA batteries, and is ready to use right out of the package. This item is suitable for use at home or while traveling.

The FL420 meets all criteria of CE and FDA standards for pulse oximeters. It is , FDA 510(k) cleared. Used by doctors and other health professionals. The FaceLake FL420 Pulse Oximeter is a painless solution for monitoring health activity in the body.

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The FL420 alarm system alerts the user to measurement readings which are outside of the range that the user has set. The built-in speaker will automatically beep when a reading is detected outside of the user's range. The range thresholds for SpO2 and pulse rate can be easily set within the pulse oximeter’s menu settings.

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Color LCD

The FL420 contains a sharp color LCD display. The screen displays the FL420’s measurements, menu system, and visualization charts. Measurements update in under 10 seconds.

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Auto-rotational Display

The auto-rotating display will automatically align to the viewing angle which matches the orientation of the device. The display will also adjust the layout of the display parameters to correctly match the viewing angle. The device can be used while holding it towards or away from you.

Warranty icon   This unit comes with a 30 day money back guarantee and a one year warranty.

  • Measures oxygen saturation and pulse rate
  • 30+ hours of continuous monitoring on one set of batteries
  • Integrated SpO2 probe and processing display module
  • SpO2 and Pulse Rate bar graph
  • Bright OLED screen displays in full color with sharp text and images
  • Low battery level indication
  • Auto power off after 5 seconds
  • Low power consumption on 2 AAA batteries
  • Interference resistance against ambient light & measurement performance at low perfusion
  • Intended use for spot check of blood oxygen levels at home or in sport/recreational use such as mountain climbing, high-altitude activities, and running
  • Custom alarms for SpO2 and Pulse Rate thresholds
  • Multi-directional display automatically rotates and can be clearly read from multiple viewing angles
  • Accurate sensor measures within ±2% or ±2bpm


  1. FL420 Unit
  2. Instruction Manual
  3. 2 AAA Batteries
  4. Carrying Case
  5. Lanyard

The device’s battery configuration is misleading; the batteries should be inserted following the ‘+’ and ‘-’ on the bottom of the battery input area, with the positive end of one of the batteries pointing to the spring                                 



Alarm Instructions

1. Press the main button when the device is in operation status to enter menus.
2. A short press on the main button will move the selection arrow. A long press on the button will enter the highlighted menu option.
3. Enter the “Alarm Set” menu to change the High/Low thresholds of the alarm, and adjust by holding the main button while a threshold limit is highlighted.                            

Extended Specifications:

SpO2: Digital
SpO2 Range: 0% - 99%
SpO2 Resolution: ±1%
SpO2 Accuracy: ±2% (70-99%), 35% - 70% unspecified
Pulse Rate: Digital
Pulse Rate Range: 30bpm - 240bpm
Measurement Performance in Low Perfusion
Oxyhemoglobin and Pulse value can be shown accurately when pulse-filling rate is 0.5%
Low battery indicator
Battery Type: AAA Alkaline batteries
Operation Time: 30 hours for normal operation
Interference Resistance Capacity Against Ambient Light
Deviation is smaller than ±1% between value of Oxyhemoglobin measured in natural lighting indoor condition and present lighting sources and of that measured in dark room
Operating Temperature: 5°C - 40°C
Storage Temperature: -40°C - 60°C
Operating Humidity: 15%RH - 80%RH
Size: 57*31*34mm
Weight: 1.8oz (50g)
Display: Color OLED
Warranty 1 Year

Customer Reviews

Based on 14 reviews
Karl Benz

FL420 Pulse Oximeter with Alarm,

3rd Purchase

Works well.

Deborah Monte

FL420 Pulse Oximeter

Barbara McGoldrick
Pulse ox

This pulse ox was delivered timely and works well!


FL420 Pulse Oximeter

Click here to see or download FL420 Pulse Oximeter User ManualIf the link does not open properly on your desktop or mobile device, please contact us.
  1. SpO2 - Digital
  2. Range: 0% - 99%
  3. Resolution: ±1%
  4. Accuracy: ±2% (70 - 99%)
  5. 35% - 70%, unspecified
  6. Pulse Rate - Digital
  7. Range: 30 - 240 BPM
  8. Resolution: ±1bpm
  9. Accuracy: ±2bpm
  10. Measurement Performance in Low Perfusion
  11. Oxyhemoglobin and Pulse value can be shown accurately when pulse-filling rate is 0.5%
  12. Low battery indicator
  13. Battery Type: 2 AAA Alkaline batteries
  14. Operation Time: 30 hours for normal operation
  15. Interference Resistance Capacity Against Ambient Light
  16. Deviation is smaller than ±1% between value of Oxyhemoglobin measured in natural lighting indoor condition and present lighting sources and of that measured in dark room.
  17. Operating Temperature: 5°C - 40°C
  18. Storage Temperature: -40°C - 60°C
  19. Operating humidity: 15%RH - 80%RH
  20. Storage Humidity: 10%RH - 95%RH
  21. Size: 57*31*34mm
  22. Weight: 1.8oz (50g)
  23. Display: Bright Red LED
  24. FDA 510(K) cleared

To receive accurate readings, please follow these tips:

  1. Low blood perfusion can affect accuracy of your readings. Warm your hands and fingers before taking your measurements by rubbing your hands together. Remember, your pulse oximeter is measuring your SpO2 and PR based on your blood flow. If the blood flow in your finger drops below a certain level, the pulse oximeter will not be able to function.
  2. It usually takes 10 seconds to get accurate readings. Some individuals may require a longer time. You may have to wait about 30 seconds for the stable readings.
  3. Keep your hand still while taking a reading - any movement can cause the inaccurate readings.
  4. Nail polish and fake fingernails may cause false readings. If possible, switch to an unpolished nail or consider another application site.
  5. Some medical conditions like atrial fibrillation (afib) and hypotension can result in inaccurate readings. We suggest that you consult a physician before use.

I have installed new batteries but the device still does not turn on. What could be the problem?

The battery placement for oximeters is different from others. Even though the two springs are on the same side, the two batteries are still required to be installed in opposite directions. The diagram shows the correct battery placement. One product image shows the batteries' installation. If your device still does not work, please contact the manufacturer to receive a free replacement.

Does it measure the heart rate?
Yes, this device would measure heart rate along with blood oxygen levels.

Are Facelake pulse oximeters latex free?
Yes, our pulse oximeters are latex free. The hypoallergenic finger chamber is made of medical grade silicone. 

Does this pulse oximeter have an alarm?
No, this pulse oximeter does not have an alarm, our FL100 pulse oximeter has an alarm.

Does this product ever need recalibration?
The finger pulse oximeter does not need any calibration. However, if you have any issues with the device, please check the user manual and Precaution or contact us. We will be more than happy to further assist.

What kind of battery does the Facelake pulse oximeter use?
The Facelake fingertip pulse oximeter uses 2x AAA alkaline batteries.

Can I use your Facelake pulse oximeter during sleep?
This pulse oximeter can not be used for continuous monitoring, and it does not have a memory to save the readings. It will give you a reading as long as you have your finger inside the finger chamber but, once you take your finger out, the pulse oximeter will turn off after 5 seconds.