Placement of Sampling Media During Welding Operations

Question of the hour: should the media be placed under the weld helmet, or on the welder’s shoulder?

The proper positioning of the sampling media, such as a 37 millimeter mixed cellulose ester (MCE) filter, is key to capturing the employee’s true exposure during welding operations. The Occupational Safety and Health Administration (OSHA) mandates that personal sampling for welding fumes be conducted with the filter placed inside the welding helmet.

The following excerpt was taken from the OSHA Technical Manual, Section II: Chapter 1, Section III, for “On-site Inspection Activities” in “Overview of Sampling Procedures”:

“For an employee wearing a respirator (including a supplied-air hood for welding or abrasive blasting), place the sampler outside of the respirator. This action is necessary to determine whether the respirator’s Assigned Protection Factor (APF) is adequate. For an employee wearing a welding helmet which is not a respirator, the collection device shall be placed under the helmet.”

The complete manual can be found here:

OSHA Section II: Chapter 1, Personal Sampling for Air Contaminants (

The excerpt above answers two common questions:

1. Where should the sampling media be placed when welders are wearing Powered Air Purifying Respirators (PAPR) with welding visors?

2. When only a standard weld helmet is used, where should the sampling media be positioned?

When the requirement is to place the media under the helmet, it requires the cooperation of the welder, and diligence by the industrial hygiene and or safety professional performing the sampling.  Repositioning of the filter may be required throughout the monitoring period, particularly after breaks, or when the welder performs other tasks such as grinding and or cutting operations.  Typically the welder will be required to use a leather or flame resistant long sleeved jacket. Once the welder dons and buttons the jacket, the sampling filter can be positioned directly under his/her chin with verification that the filter cassette is actually under the helmet by having the welder drop his/her helmet. 

Anyone who has performed personnel exposure monitoring on welders can attest to the following observations:

1. The subjects of the sampling are not always the most receptive to having to wear a personal sampling pump for the duration of their workday.

2. Depending on the tasks they perform, the subject does not typically perform welding in a stagnant body position.   They may in fact, consistently change positions throughout the shift.  Repositioning and even replacing filters that have “popped off” may be required.  Be sure to instruct the welder that if the cassette becomes dislocated they should not try to reattach it, but should let the IH know.

3. Welders may not be readily receptive when the IH has to continually reposition the filter and hoses to ensure the filter remains in the proper position. However, problems may be alleviated by explaining to them the importance of properly positioning the cassette to ensure that a true exposure sample can be obtained.

In the past, we have used other means to collect personal samples on welders during welding operations.  The filter cassette can be changed from 37 millimeters to 25 millimeters.  The filter cassette diameter allows for less disturbance to the welder. Remember that during heavy welding operations, the 25 millimeter cassette may need to be changed out more than once per shift, due to the possibility of the filter media being overloaded by the welding fume. Check with the AIHA accredited laboratory you will be using for the analyses to help determine the maximum filter loading levels.

Lastly, there are additional sampling tools that are becoming available. This includes a weld helmet attachment whereby the sampling pump tubing can be attached inside the welding helmet and the filter cassette hung from the helmet’s head suspension or clipped to the side of the helmet.  I personally have not used this type of attachment and cannot speak to the ease of use or effectiveness of this alternative.

Numerous available references indicate that overall worker exposure to metal fumes generated during welding operation, are lower when measured inside the weld helmet as compared to outside the helmet. A few of these references include:

Johnson, W.S.: An Investigation into the True Exposures of Arc Welders by Means of Simultaneous Sampling Procedures. American Industrial Hygiene Association Journal 20:194-196 (1959).

Goller, J.W.; Paik, N.W.: A Comparison of Iron Oxide Fume Inside and Outside of Welding Helmets. American Industrial Hygiene Association Journal 46: 89-93 (1985).

Mike McElhinny, CIH
Senior Consultant/Project Manager
Phone: 814.408.4711