Think you may have occupational asthma? Accurate diagnosis may include methacholine fumes

Occupational asthma [spasms and muscle constriction of the lung’s air passages] is caused by, or worsened by, inhaling substances on the job, such as chemical fumes, gases, or dust.

It causes tightness of the chest, wheezing and shortness of breath.

Images of spirometers produced by Google image search

There are many types of spirometers.

When other diagnostic tests are indefinite

Doctors may use spirometry, the measurement of breathing capacity of the lungs, to aid in the diagnosis of asthma.

[They use spirometers to measure the movement of air into and out of the lungs. As shown in the photo, spirometers come in many forms.]

But sometimes asthma is difficult to correctly diagnose because spirometry and other diagnostic tests have neither confirmed nor eliminated it.

A challenge for your lungs

The methacholine challenge test is often used to eliminate asthma as a diagnosis.

The patient inhales a calibrated saline mist that contains the chemical methacholine chloride.

Medical personnel use spirometers and the reaction of the patient’s lungs to the methacholine chloride aerosol to help determine a correct diagnosis.

Technicians who administer the challenge need protection

Because methacholine is administered in an aerosol mist inhaled and exhaled by the patient it may spread throughout the lab.

Depending on the design of the room’s ventilation, the mist may be unintentionally inhaled by technicians, too.

If they frequently administer the challenge, over time they can develop occupational asthma, too.

Controlling exposure to methacholine

Thoracic medical practices often develop protective strategies that involve source capture of methacholilne fumes.

‘Source capture’ is known in industrial hygiene circles as local ventilation to capture hazardous workplace substances before they can spread throughout a work area.

They may choose a Model 300 tabletop fume extractor to install exactly where it can capture a patient’s exhalations.



If the methacholine challenge is administered in several rooms throughout the facility, they may choose a portable Model 300, which has wheels and handle for easy transport.

Both models can be equipped with HEPA filters, which has an efficiency rating of up to 99.97% on particles 0.3 microns and larger.

Feeling challenged?

If you’d like to discuss the challenges of chemical fumes and mists in your workplace, give us a call at (800) 799- 4609. You can also visit our website, email, or fill out the feedback form below.




Occupational Asthma

Guidelines for Methacholine and Exercise Challenge Testing-1999

Insert for methacholine chloride powder