Negative pressure versus powered air purifying systems

Responding is Josie Larsen, market analysist, RPB Safety LLC, Royal Oak, MI.

Before we decide the better of the two options, we should understand how they work and their limitations.

A negative pressure device depends on the operator to breathe through a filter to purify the air. It could be a disposable respirator, a half-mask respirator or a full facemask. The latter two devices could offer protection against particulates, gases, vapors or a combination of these, depending on the filters used.

A powered air purifying system will offer the same protection as a negative pressure device with the same range of filters offered. The only difference is that a powered system uses a motor, battery and fan to do the work for the wearer.

A negative pressure device typically requires the wearer to use other forms of face protection such as eye protection, head protection and hearing protection, or a combination of them depending on the task. The challenge here is compatibility: Eye protection and face protection normally mist up when using such devices. Similarly, they can break the seal of the mask, rendering it useless. In addition, a negative pressure device is dependent on the wearer being clean-shaven.

It takes a lot of effort to draw air through a filter to make it work. Some countries even require that workers wearing negative pressure devices for longer than an hour should take a 15-minute break. It is not considered safe for an employee suffering from asthma to use this type of device because it could cause undue pressure to the heart.

A powered air system can offer complete head/eye/hearing and respiratory protection with total compatibility. Similar to a negative pressure device, it draws the contaminated air through filters that purify the air. However, this system uses a fan to do the work for the wearer, enabling the wearer to complete the task with minimum effort.

Many different systems are available on the market. Each would be selected for the task required:

• A general-purpose system could offer either soft-top or full head protection. It could also use earmuffs, offering a range of hearing protection. Some systems have a polycarbonate visor, enabling it to protect both the face and the eyes. Finally, it offers a range of filters, enabling it to protect against particulates or gases and vapors.
• A welding system could offer all the above but also have interchangeable lenses required for welding operations.
• A paint spray system that has replaceable peel-off visor strips to ensure the painter has good visibility.

To sum up what a powered system offers that a negative pressure device doesn’t:

• Complete compatibility with all head-worn PPE without affecting performance
• Reduced fatigue to the operator, allowing him or her to focus maximum effort on the job
• Elimination of the need to supervise for facial hair

In essence, a powered system will offer the employee true comfort and offer the employer peace of mind and ultimately advance safety and increase productivity.

Editor's note: This article represents the independent views of the author and should not be construed as a National Safety Council endorsement.