This problem could include a number of variables, but most likely would fall into three categories: machine fault, adapter/mask fault, or subject/operator error. If it’s a one-time problem when you are able to pass other people, the answer simply may be that the mask is not a good fit on the subject. When several subjects can’t pass, you must look at the other variables.

Machine Fault:

  1. You must do the daily calibration at the beginning of each day.
  2. If the Quantifit successfully completes the dual tube calibration without an error message, this assures that the machine is operating properly and within tolerance.
  3. If the Quantifit does not complete the dual tube calibration, service might be needed. Please contact OHD customer service.

Mask/Fit Fault:

  1. You must first determine that there is a proper fit. Any facial hair, hair getting anywhere under the mask seal, temple hair too far forward, sunken temples or facial scarring, protrusions or blemishes, having the mask too loose or too tight, can all be reason enough to keep the Quantifit from pulling a negative pressure within the mask. There are other obstacles that can come into play which are too numerous to list. With more experience fit testing, it’s easier for one to see potential problems with fit.
  2. To further check on the mask fit, do a user seal check for 10 seconds. Press the Seal Check button and take in a breath allowing for plenty of suction on the mask. If after 10 seconds the mask “drops” when releasing the Seal Check button, then there was a good seal in place. If there is no felt movement when the Seal Check button is released, then the air has leaked out in those 10 seconds.
  3. Exhalation valves may be dirty or creased allowing air to be pulled into the mask. While the inhalation valves must be removed or propped open, the exhalation valve must remain in place and maintain a good seal.
  4. On the mask, the apex of the head straps should sit on the crown of the head and not off to one side or the other.

Adapter Fault:

  1. The adapters must be kept clean and in good shape.
  2. Disconnect and reconnect all tubes to make sure they all “snap” into place for a secure connection
  3. With a Phillips-head screwdriver, lightly turn the screws on the perimeter of the blue tube side of the adapter. These screws are glued into place, but can become loose over time.
  4. If the adapter had been dropped or crushed, a hairline crack might cause leakage.

Operator/Subject Error:

  1. Holding breath. The most obvious error that could take place is when the subject does not remain completely still. He or she must be instructed to hold breath, keep lips and teeth together, no swallowing, etc. Tell the subject to hold a comfortable breath. When holding a deep breath, there is more air fighting to get out of the lungs, and this could cause movement or actually be more of a challenge for the subject to hold. The Quantifit is very sensitive and will even register slight head movement.
  2. If the Trigger button is pressed while the test subject is still breathing or inhaling, the Quantifit will display a message stating that the breath must be held before the measurement can begin.

If it’s only one or two people who won’t pass, but others are passing, this would indicate:

  1. A poor fit, try a different size or brand of mask.
  2. Hair, not clean-shaven, scar, or some other impediment may be breaking the surface of the mask.
  3. Test subject not holding breath properly.
  4. In rare cases, the test subject might have a hole or defect in his or her eardrum.
  5. Dirty mask/inhalation valve. Even if the valve does not look dirty, wipe the inside of it with a wet finger or cloth.

If there is an inhalation valve inside the mask where our adapter connects to the mask, this will definitely interfere with the testing procedure. To begin the test, the Quantifit first exhausts air out of the mask to get to the target negative pressure. If the inhalation valve is in place, the Quantifit will not be able to pull air out of the mask because the suction will pull the valve shut. This usually shows up on the graph as a lot of up and down movement when the test begins.

If it’s easy enough to remove the valve and replace it, we suggest doing this. If it’s difficult at all, you can prop open the valve before the test. If you have a two-adapter kit, the critical one is the side with the two ports on it. We sell a Valve Prop that can be used to keep open the diaphragm. If you do not have a valve prop, a good substitution would be to cut a drinking straw to approximately two inches. Fold this in half so that it makes a V. Insert the open end of the V into the spoke-wheel gasket that holds the diaphragm in place. You can achieve the same results with a rolled-up piece of paper.

Of course, you’ll want to remove this prop after the test so that the mask is back in its original form.

OSHA 1910.134 Appendix A:

“4. (a) (4) The respirator filter or cartridge needs to be replaced with the CNP test manifold.
The inhalation valve downstream from the manifold either needs to be temporarily removed
or propped open.”

Quantifit eliminates the need to delay testing on mask users that have just eaten or smoked. You can test immediately with Quantifit. The Quantifit CNP technology enhances logistics by simplifying employee requirements prior to testing.

The Controlled Negative Pressure technology of the OHD Quantifit allows the mask to be challenged in ways that are impossible, or at least impractical, for other systems. Because we use negative pressure to replicate the negative force of inhalation, the OHD Quantifit can be set to increase the negative force in the mask to replicate breathing rates of over 100 liters of air exchanged per minute and measure the leak effect in only 8 seconds. Other systems might only be able to test at this level if you get the wearer to actually breathe at this high rate continuously for several minutes. Doing so with other systems would create great stress on the mask wearer!

See tech sheet

Yes! Once in a while we see individuals who cannot pass a test because their ear drums are perforated. This is an unusual circumstance, but it does happen. This is usually evident by a traceline that moves up and down throughout the test.

First, verify that the subject is actually holding his breath by closing the airway. Instruct subject to press tongue firmly against and towards the back of the roof of mouth. This will help close the throat completely and assure an airtight seal.

Second, examine the obvious causes for leakage which include facial scars, beard or stubble, exceptionally thin face or indented temples, hairline intercepting the seal of the mask or the mask pulled too tightly producing skin puckering around the seal.

After you have eliminated these as a possibility it is time to consider that the subject may have a perforation in the ear drum that is resulting in a leak to the mask.

If there is a perforation, there would be a clear passage way from the inner ear through the Eustachian tube and into the sinus cavity. A perforation in the ear drum (tympanic membrane) would open the ear to the outside and thus be measured as a leak. A way to confirm this is to have the employee insert tight-fitting ear plugs and perform another fit test. (If ear plugs are not available, the employee could put fingers in their ears to block the possibility of air flow.) Perform another fit test, and if the fit factor passes and is significantly higher, this would suggest leakage through the ear.

A person passing the fit test while wearing ear plugs should also utilize the ear plugs while wearing the mask in a real work environment. An open passageway through the ear can potentially introduce harmful vapors into the sinus cavity and beyond.

Click Here for tech sheet

A fit factor is defined by OSHA as the ratio of the modeled breathing rate to the measured leak rate.


Additional details on OHD’s LOGIC Software coming soon.


When the operator is experiencing difficulty getting anyone to pass on these masks, the answer typically lies within the Scott Connector, p/n 200423-01. It is recommended that the operator keep a spare part, and replace them at minimum once each year.

Please follow these instructions when fit testing withthis Scott Connector with our Kit #1 part number 9513-0130.  

  1. The connector must be modified to be used for fit testing, and once modified, it must not be used during the need for a respirator.
    1. There are two valves that must be removed, a clear circular valve on the bottom, and the valve that can be seen when looking into the opening where the OHD adapter will be threaded into.
    2. The threaded opening must have a rubber washer, but you must be able to clearly see into the connector.
  2. The exhalation valve is dirty
    1. This can occur even when the part is brand new
    2. You must remove teh rubber housing that protects the exhalation valve.
    3. With water or a mask wipe, clean the underside of valve as well as the circle on which it rests
  3. Foam pad is worn out
    1. Over time, the foam pad that creates the air-tight seal against the mask, can lose its cushioning ability over time.
    2. This foam pad can lose elasticity whether it is being used or not, and many times is revealed when a company begins the fit testing for the year.
    3. The concnetric circles where the pad connects to the mask, get more and more compressed over time and lose their air-tight function.
    4. If the company has a certified Scott technician, the technician can replace the foam pad. If not, the entire part must be ordered.
    5. One sign that the foam rubber is too old, is when a first step or first person might pass, but every following test produces a failure.

Click Here for tech sheet

Please follow instructions when using Draeger Mini Rap connector 4055505 with OHD Kit #1 (9513-0130) fittest adapter.

This combination will work with any snap-in connection on a Draeger respirator.

To prep the Rap Adapter, you must remove the spokewheel (1) on the threaded side, remove and discard the flat diaphragm (2) and then reinsert the spoke wheel gasket (3).

The Kit #1 adapter will screw into the threaded side of the Mini Rap adapter, and opposite end of the Rap (with the O-ring) can be inserted into the front of the respirator until it clicks into place.

The only maintenance required on this Rap adapter is to be sure the rubber gasket remains clean. This part will last for many years with normal use.

The Inhalation valve must be removed from the ISI part #171138. (Image shows part without diaphragm.) This is an orange/red diaphragm that is attached to the under-side of the cross-hair plastic.

The 171138 must be attached to the front of the respirator. First you will remove the front portion of the respirator by unscrewing the 4 screws. The inside hex nut uses a 5/16 nut driver and the outside uses a 3/32 allen wrench. The 171138 will replace the front portion of the respirator.

After the 171138 part has been attached to the respirator, prop or remove the inhalation valve, then attach Kit #1 into the female threading.

Since this ISI piece is not easily moved to another respirator, ideally you will want to have surrogate masks in each size of the respirator. The OSHA fit test requirement is that you must have one of each size for the test subject to try.

Click Here for tech sheet

Testing the MSA Ultra Elite respirators requires the OHD Kit #38, 9513-0380.

  1. Regulator must be removed from mask for fit testing.
  2. Insert adapter into the front opening of the mask, and the O-rings will create an air-tight seal. (Fig. 1)
  3. The silver prongs will prop open the inhalation valve to prepare the mask for testing. Do not twist the adapter on the mask or it could do damage to the gasket in the mask.
  4. Connect the clear tubes to the two-connector side and the blue tube to the single- connector side (Fig. 2)
  5. Perform fit test

There are two things to look for if you are having trouble getting people to pass with this respirator.

  1. Make sure that the bottom of the adapter says “Rev B.” If it has no Rev, or Rev A, Contact OHD to update your adapter.
  2. When the adapter is twisted onto the side of the mask, there is a natural stopping point. You must then turn harder so that it will travel another quarter inch. If left at the first stop, the adapter will not make an airtight seal.