How to replace an Oxygen Sensor in an MSA Altair 4

Got a MSA Altair 4 that gives you an O2 Sensor Error?


Let's fix it!

Step 1:  -  Remove the cover

We'll start by removing the screws from the back cover of the MSA Altair 4. Be careful some of these units will have a very tight seal, and may require a little finesse and persuasion. 

Step 2:  -  Reinstall the gasket

This is pretty common on MSA Altair 4, the rubber gasket will stick to the sensors, or it will fall out. The best thing to do is remove it, and reinstall it on the front cover.


Now you see all of the sensors, you can easily identify which one is the oxygen sensor.

Step 3:  -  Remove Sensor

Let's remove the MSA Altair 4 Oxygen Sensor, you shouldn't have to pry, or pull too hard. Most of the time a little wiggle, while pulling does the trick. After the sensor has been removed, you might want to record the serial number and date code from the old sensor. This is a good way of maintaining records of sensors that have been replaced, you should also record the new oxygen sensor serial number and date code. They have a lifespan of about 2 years. 

Step 4:  -  Install Sensor

Time to install the new oxygen sensor in the MSA Altair 4, DO NOT try to force the sensor in the socket, it should almost fall into place, after positioned correctly. Once it is in position, apply a very small amount of pressure to ensure proper seating of the new MSA Altair 4 oxygen sensor.

Step 5:  -  Reassemble the MSA Altair 4

Now it is time to put MSA Altair 4 back together, however new oxygen sensors will need to be acclimated to the unit. We typically wait 20-30 minutes, the unit can on or off, but if it is turned on it will be in alarm mode and the reading will be wrong. I normally install the sensor, turn the unit on and wait for the O2 reading to stabilize.



Step 6:  -  Wait and Zero

Once, the MSA Altair 4 is stable and the O2 reading isn't jumping around, it's time to perform a Zero Calibration, to perform this operation press and hold the right button until you see the following screen thats reads "Zero Cal?". Confirm you want to perform a Zero Calibration by pressing the center button. The next screen is Span Calibration, it is a must that the MSA Altair 4 unit be recalibrated after the new oxygen sensor is installed. However we are skipping this step and we have a calibration guide here. After everything goes through the new oxygen sensor should be reading 20.8% on the MSA Altair 4


How to Calibrate the MSA Altair 4 gas detector

Use this calibration gas:

20ppm Hydrogen Sulfide
60ppm Carbon Monoxide
58% LEL Pentane (1.45% Volume Methane as a Simulant)
15.0% Oxygen
Nitrogen Balance

Want to calibrate the MSA Altair 4 or MSA Altair 4X? Here's how:
1. Turn the MSA Altair 4 and MSA Altair 4X on in normal reading mode. Do this by pressing and holding the center button.
2. Once the MSA Altair 4 and MSA Altair 4X is in normal reading mode, you need to send it into calibration mode. Do this by pressing and holding right beeps at you and the screen asks you to zero the monitor (sensor refresh on the MSA Altair 4X).
3. Now that the screen is asking for confirmation, press the center button once to confirm. This will send the monitor into zeroing mode. Now is a good time to set the monitor down, and grab your calibration gas, regulator, and calibration adapter.
4. Open the valve on your regulator. This is a very important step so you do not ruin your calibration gas cylinder. Now screw it in to your calibration gas cylinder. Close the regulator once you hear gas spewing out of it. This is the signal to know your regulator is good to close. Continue screwing in the regulator until it stops. Do not overturn it.
5. Attach the tubing to the hose barb on your regulator. Make sure the tubing is also connected to your calibration adapter.
6. Wait for the screen to come up asking for you to apply calibration gas. Once this screen comes up, press the center button again to confirm. Screw the calibration adapter in to your gas detector. Once it is screwed on, turn on your gas.
7. Make sure your calibration gas values on the screen match what is on your calibration gas cylinder!
8. Once the calibration procedure is completed, turn your gas off and remove the calibration adapter from the MSA Altair 4 or MSA Altair 4X. The screen will go back to normal reading mode within a few seconds.
9. Congratulations! You have officially calibrated your MSA Altair 4 or MSA Altair 4X gas monitor. Make sure to record these readings in your calibration log!