In Parts 1 and 2 of this series, I outlined the pros and cons of using low-cost visual training aids (black and white boards and flip charts) when presenting to a small group of people in a small venue. If you're presenting to a large group in a large room, you should consider more sophisticated options. That would include mechanical training aids like overhead projectors and computer-projected images and software, such as PowerPoint™.

Advantages & Disadvantages of Overhead Projectors

Overhead projectors have been used as an electronic version of the flip chart and they do resolve most of the problems associated with flip charts. When overhead projectors first came out, many presenters wrote the transparencies by hand. Printing the transparencies took some work. But today it's relatively easy for presenters to use personal computers to print not just text but computer graphics onto their transparencies for a more professional look.

Advantages

• Projected images can be enlarged, making images visible to large groups.
• Projectors can be used in fully lit rooms.
• Transparencies are relatively inexpensive to produce.
• Transparencies can be handwritten or computer-generated.
• Color can be used on transparencies, for emphasis.
• Transparencies can include motion.
• Transparencies can be reused and changed easily.
• Use of transparencies enables presenters to face the audience.
• Pre-prepared transparencies can be used as handouts.
• An assistant can change pre-made transparencies, enabling the presenter to focus on the presentation and the audience.

Disadvantages

• Handwritten material can look sloppy if not pre-prepared.
• Overhead projector and screen are needed.
• Lamps can burn out and interrupt a presentation.
• Presenter and audience can be distracted by the light's glare.

How to Use Overhead Projectors Correctly

To maximize your use of an overhead projector, here are four tips:

1. Be Prepared

• Pre-make all transparencies using computer-produced images.
• Before your presentation, set up the projector and screen, and test all equipment.
• Have a spare lamp and know how to change it. Remember the lamp may be hot and you should not touch a quartz lamp with your bare fingers.
• If you're using transparencies that have a backing paper attached, separate the paper from the transparency before your presentation. Doing this during the presentation wastes time and distracts the audience.

2. Strategically Position Equipment & Yourself

• To prevent keystoning of the image, tilt the top of the screen slightly forward to keep the screen surface parallel with the overhead projector lens.
• Use a table that is large enough for the projector and two piles of transparencies. During your presentation, take unviewed transparencies from one pile and place viewed transparencies in the other.
• Don't block the screen from your audience. Try to seat everyone so they have a view of the screen, and then try to stay out of their way. If necessary, place the transparency on the projector stage and step aside. Talk from the side of screen, facing your audience.

3. Avoid Glare

• Use transparency frames. This cuts extraneous glare from the lamp. You can also write notes to yourself on the edge of the frames.
• Slide one transparency over the one you are removing to avoid a flash of light between transparencies.

4. Keep the Audience's Attention

• Use a sheet of paper over the transparency to hide information so that your audience will focus only on one item at a time. You will be able to see what the next point is through the paper.
• Use a pen or pencil to point to images on the transparency rather than pointing to the screen. This way you can face the class and not have to move around as much.
• Use color to highlight important points.
• If you need to refer back to a particular transparency for review, turn it perpendicular to the rest of the pile so that you can get to it easily.
• When talking to the audience, turn off the projector so people pay attention to you.

Conclusion

In next week's final installment of this series, we'll discuss computer-projected software, including PowerPoint™.

EDITOR'S NOTE

Canada Observes Remembrance Day

Tomorrow is November 11. Many members of SafetyXChange will likely understand the significance of this. It was on this date in 1918 that representatives of the German government signed the armistice ending World War I. In Canada, November 11 is known as Remembrance Day, a time to pause in a silent moment of remembrance for the men and women who have served the country in war and peace.

(In the US, November 11 is known as Veterans' Day. But it's on Memorial Day that Americans honor their fallen soldiers.)

For our Canadian members of SafetyXChange, here's a small piece that we believe is appropriate for the occasion.

Glenn S. Demby
SafetyXChange
Editor-in-Chief

MILITARY PPE

The Macpherson Respirator: The British Army's first general issue gas mask.

The Macpherson Respirator

By Catherine Jones

Gas masks have been around for a long time. In 1799, Alexander von Humboldt produced a rudimentary gas mask for use by miners. Firefighters began using the mask soon after.

The gas mask became a piece of military equipment in World War I. At the start of the war, the armies of the combatant nations issued masks to protect soldiers against carbon monoxide emitted by unexploded shells. CO concentrations were particularly dangerous in the trenches and confined spaces where the soldiers spent most of their time.

Sadly, gas masks would soon be put to a new use. On April 22, 1915, the German army introduced the use of chlorine gas as an offensive weapon during an attack in Ypres, Belgium. Soon, both sides were using it. The first gas attacks caught the armies unprepared. Canadian soldiers, for example, were advised to urinate on rags and hold them to their face.

The Macpherson Respirator

Both sides worked feverishly to develop more effective protections against gas attacks. Dr. Cluny Macpherson, a gas advisor from Newfoundland who was stationed in Gallipoli, Turkey, designed a system to protect soldiers. Macpherson's invention was a canvas hood treated with chlorine-absorbing chemicals and fitted with transparent plastic eyepieces.

As the war progressed, the gas mask was modified to defeat other poison gases used, such as phosgene and chloropicrin. But the Macpherson "smoke helmet" is considered to be the first gas mask to protect against chemical weapons.

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