Grantville Gazette, Volume VIII Page 23

  This is not, of course, a method which would be acceptable in a modern acoustics laboratory. But it is way beyond anything the down-timers had.

  Ultraviolet radiation. The ideal UV meter would be a photoelectric device, based on silicon carbide or aluminum nitride, or perhaps a gas-filled tube. Laboratory UV detectors are unlikely to be available in Grantville. Some fire detectors are sensitive to UV-B and might be adaptable to goggle testing use.

  There are probably sources of UV light in Grantville. These will mostly be sources of long-wave UV, the "black light" tubes used for shows and so forth. However, rockhounds and geology classes may have short-wave UV lamps.

  Next we need a detector. It could be an up-time "glow-in-the-dark" decoration. Or it could be a fluorescent mineral, from an up-time rockhound collection, or found fortuitously after the RoF. Again, it is probably easier to find materials which fluoresce strongly when exposed to long wave UV. In essence, we are looking for glasses which, interposed between the light and the fluorescent material, prevent the fluorescence by blocking the light.

  Safety Assurance

  Safety is assured by three different means: engineering controls, administrative controls, and personal protective equipment.

  Engineering Controls

  Engineering (environmental) controls are facility, process and machinery changes which reduce exposure to hazardous conditions. They can modify operating conditions so that the hazard is less likely to arise, less severe when it arises, or more quickly dispelled. Or they interpose a barrier between the worker and the hazard. Finally, they can at least give warning that a hazard has increased, so workers can don protective equipment, leave the work area, or take corrective action.

  Engineering controls of the first category include

  —use of safer raw materials (e.g., eschewing lead and mercury).

  —wetting systems to control dust

  —assuring adequate lighting, temperature control, ventilation (vents, fans, and fume hoods), and waste disposal

  —designing machinery controls ergonomically to reduce repetitive stress injuries.

  Barriers take several forms. First, there is the process enclosure; the potentially hazardous process is conducted inside a closed environment, so that exposure occurs only during raw material replenishment, product removal or maintenance, or if it a leak occurs. A variation on this is one in which the process is partially enclosed, and workers pass in and out of a controlled access point designed to mitigate the escape of hazardous materials into the larger environment. If the hazard is stationary, like a machine workstation, then it is sufficient to keep the worker out of harm's way by means of a guard rail or safety interlocks.

  Secondly, there is the operator enclosure; the worker is placed in a protective control room or cab.

  Thirdly, there can be mobile barriers, usually linear, that can be placed in the likely propagation path of the hazard. For example, one can place heat shields, steam curtains or air jets in front of radiant heat sources.

  Warning devices include leak and smoke detectors.

  Engineering controls may have existed earlier (e.g., shoring up the ceiling in a mine, but they became more common in the nineteenth century: white phosphorus matches were banned in Denmark in 1872 (Emsley); machinery guards were required by Great Britain, and ten American states, by 1897 (MacLaury).

  * * *

  Ventilation. Natural ventilation is achieved by providing permanent openings to the outdoors, or by opening doors, windows and vents. Engineers need to worry about making these easy to open and close (especially if out of reach), and making it easy for air to pass through them (e.g., by aiming the vent or adjusting a window wing). Exhaust pipes can be equipped with deflectors to increase draft. Equipment is arranged so as not to obstruct airflow.

  Artificial ventilation is designed to exhaust (or clean) contaminated air, or to bring in fresh air. It will probably involve some kind of fan and there may also be a filter to remove dust.

  If the hazard is localized, an exhaust hood may be positioned above the source, an air douche may be used to blow fresh air at the exposed worker, or an air curtain can prevent air exchange between the contaminated area and the work zone proper.

  Heating. Heating systems can be central or local, and will probably involve circulation of heated air, hot water or steam. These pose hazards in their own right.

  Illumination. Natural illumination can be provided by windows or skylights. The introduction of a better quality of glass will increase light transmission. Natural illumination is often problematic if there is a need to control temperature. Night work indoors, of course, necessitates artificial illumination.

  Artificial illumination as of RoF took the form of torches and lanterns, which in turn presented fire hazards. In OTL, subsequent developments include the gas lamp (1792), electric carbon arc (1809), limelight (1826), kerosene lamp (1853), electric filament lamp (1870s), mercury vapor lamp (1901) and fluorescent lamp (1937). Electrical illumination will require either batteries or a power generation and distribution system.

  Reflectors can be used to make more efficient use of the available light sources.

  Noise Reduction. Obviously, you can say that factories are already loud; if it bothers the worker, let them wear earplugs.

  But the other approach is to reduce noise generation and transmission by various engineering expedients.

  You start by eliminating noise at the source.Noise can be abated by use of equipment substitution (presses instead of hammers, belt drives instead of gears, "mute" plastic contacts instead of metal ones, rotating rather than reciprocating mechanisms), process substitution (non-percussive processes instead of percussive ones, welding instead of riveting), preventative maintenance (lubrication, replacement of worn-out parts), and anti-vibration design (lower rotational speeds, vibration dampers, altering the vibrating member).

  If that isn't enough, you need to reduce sound transmission (soundproofing rooms, placing individual machines in enclosures, baffling equipment). Soundproofing involves the reflection or absorption of sound. It can be done locally (a machinery enclosure) or more generally (a wall between a noisy room and the rest of the factory).

  Administrative Controls

  These control who performs the work, and when and how. One might think that workers would logically do the work in the safest possible way, unless required by supervisors to do otherwise, but that ignores economic realities. During the nineteenth century, payment on a piecework basis encouraged workers to adopt unsafe practices if it would speed up their work. For example, nailers didn't wet down their cutting machines to reduce dust, because dry cutting was faster. (Sellers 26).

  Administrative controls begin with screening prospective workers to make sure they have the mental and physical capacity to perform the work without special risk. The workers may have to meet minimum age or height requirements, and be free of lung or heart disease, or back trouble, or particular allergies. After hiring, they may be required to undergo periodic medical checkups to make sure that they are still fit. This surveillance will also spot deterioration of health as a result of exposure to workplace hazards, expected or unexpected.

  It is important not to leave the examination to worker discretion. Even in the nineteenth century, peer pressure, as much as job competition, discouraged workers from taking time off from work because of occupational disabilities. (Sellers 23). Physicians were consulted only once the worker was seriously ill. This wasn't just a matter of economics; the competence of doctors was questioned (24).

  When the company physical was first introduced, there was considerable worker resistance. The workers believed that the exams were a subterfuge, used to "weed out union sympathizers from the workplace." Or at the least, that the company would refuse employment to the old or infirm merely because of the "compensation risk" they posed. (119). The burden on government and industry will be to persuade workers that the examination is to their ultimate advantage. Even — or perhaps
especially — when the employee is on the slippery slope of some occupational disease (24).

  Once the worker is on the job, work rules (or laws) limit the number of hours worked each day, and the length and frequency of rest breaks. The employees may be rotated in and out of particularly hazardous assignments to give their bodies a chance to recover from unavoidable exposures.

  Administrative controls also include worker training in how to perform the work and how to respond in an emergency, signage to remind the employees, and penalties for lapses. In a steel plant, workers might be required to drink plenty of liquids to reduce heat stress. (Given that Grantville is now in Thuringia, Germany, I suspect that the liquid imbibed will be beer, not water.)

  Personal Protective Equipment (PPE)

  The most obvious means of protecting workers is to armor them in some way against the hazards, whether they be physical, chemical or biological. OSHA considers this to be the final line of defense, and would prefer that the hazards be minimized by other means first.

  Let's review the issues and options, from head to toe. Before we get into the details, one caveat: don't use this article as a guide to what is appropriate personal protective equipment in the modern workplace!

  * * *

  Head Protection. Soldier have worn helmets since ancient times, to protect them from inconsiderate blokes swinging maces in their direction. The "hard hat" is the construction workers' standard head protection. The original ones, patented by Bullard in 1919, was made from steamed canvas, glue, and paint. They were called "hard boiled hats" because that is exactly how they were made. Later models were made of aluminum, fiberglass or plastic.

  Hard hats consist of a hard shell and a resilient suspension. The shell helps spread the shock over a larger area, and also flexes a bit to absorb some of the impact energy. The suspension elevates the shell so it is not in direct contact with the top of the worker's head. Since the suspension is made of an elastic material, it absorbs more of the impact, as it grudgingly compresses in response to the blow. If the shell still is forced down against the skull, at least it will be moving more slowly.

  In the 1632 universe, we can certainly make hard hats. The main disadvantage is that these are likelier to be heavier and hotter than their up-time counterparts. For several years, at least, the shell will be metal, not plastic; the suspension, leather or fabric, rather than nylon.

  Hard hats were one of the first up-time articles to be closely inspected by down-timers. In Douglas Jones, "Schwarza Falls" a down-timer reported to his lord: "... one of the men let me try on his helmet. It was very light compared to what I expected, not metal, but something much lighter and yet harder than leather. The helmet did not rest on the head, but was supported away from the head on a clever network of straps. I feel that a blow to the helmet would not be felt directly, not with those straps in place."

  * * *

  Ear Protection. Ear protection dates back to Homeric times. After all, Odysseus had his crew put wax in their ears, so they couldn't hear the seductive song of the sirens. Ornamental earplugs, made of clay, ivory, amber, glass, and metal, are known from archaeology.

  The loudness (power) of a sound is stated in decibels, compared to a reference sound level. If sound A has a level which is 10 decibels higher than sound B, then A is ten times the power. A twenty decibel difference would imply that A was one hundred times the power. And so on. If the threshold of human hearing is called zero decibels, then a sound which is 70 decibels, or louder, is capable of causing harm, at least after prolonged exposure. According to EPA and NIOSH, safe exposure is limited to 24 hours at 70 decibels, 8 hours at 85 decibels, and 2.5 hours at 90 decibels. The acute pain threshold is 130 decibels; eardrums rupture at 190 or so decibels; 200 decibels can kill.

  The sound power is proportional to the square of the sound pressure (what the monitors actually measure), so a tenfold increase in power corresponds to a 3.16-fold change in pressure. Our subjective perception of loudness is a function of intensity, duration and even frequency. A tenfold increase in power corresponds to roughly a doubling of the loudness.

  By way of comparison, a vacuum cleaner at one meter produces 80 decibels, a loud factory, 90; a jackhammer at two meters, 100; a rock concert, 120; a fired rifle at one meter, 140.

  The standard personal protection against industrial noise is the earplug. A cord comes in handy for pulling the plug out of the ear canal. Modern earplugs are made of foam (polyvinyl chloride or polyurethane), and reduce noise levels by 25 decibels. A heavier-duty alternative is the around-the-ear acoustic earmuff, with additional sound-attenuating material.

  Foam isn't going to be readily available (until we restart the plastics or rubber industry), but cloth earmuffs should do. Again, the problem is that they are going to be bulky and hot. The ideal material is the one which provides the most sound absorption for the least weight. In general, the best materials are likely to be those which have a complex porous structure in which sound can be trapped, as it is in foam.

  Most of the published data on sound absorption relates to building materials, and those are given a noise reduction coefficient (the average of the absorption coefficients at frequencies of 250, 500, 1,000 and 2,000 Hz). The frequency range of human hearing is about 20 to 20,000 Hz.

  * * *

  Eye Protection. Even in modern America, there are about two thousand eye injuries in the workplace every day. Sixty percent occurred to workers without any eye protection, the other forty percent to those wearing inadequate protection (usually eyeglasses without side shields).

  According to a 1980 BLS study, about 70% of the accidents are caused by flying or falling objects, and about 60% of these were smaller than a pinhead. Some operations naturally produce dust or chips. Dangerous fragments can also be generated by explosions and breakage. Another 20% of the eye injuries were the result of contact with chemicals.

  If the hazard is purely mechanical, then the key concerns are impact resistance and coverage. By coverage, I mean that you are protected against attack from the flank as well as the front.

  With radiation, the intensity of the radiation has to be reduced to tolerable levels, without completely blocking your view of the workplace.

  Safety glasses and goggles are the primary eye protection. Goggles are better because it is more difficult for the particles or chemicals to get around them. Face shields may be added to provide an outer line of defense, and also protect the face.

  Any eye protection must be transparent, which pretty much limits the choice of material to glasses and plastics. Until we rebuild the plastics industry, we will have to use glass. That is unfortunate, because polycarbonate has about ten times the impact resistance of hardened glass.

  Case-hardened (fully tempered) glass is ordinary soda lime glass which has been heat-treated so that the surfaces cool before the interior, the surfaces thus being forced into compression. Its missile resistance is about twice that of ordinary glass (measured as the impact velocity causing fracture). If the glass does break, it "dices" into small fragments with rounded edges.

  A second kind of safety glass is wire glass, essentially, sheet glass with an internal metal mesh. It is used mostly in fire doors and the like, because the glass remains in place even when cracked by the heat of a fire.

  Neither is anywhere near as good as polycarbonate. So we will have to compensate by using thicker lenses. What about "bullet-proof glass," you ask? It is actually a laminate of glass and polycarbonate.

  Testing for impact resistance is straightforward. You start with a drop test. The ANSI standard is a one inch diameter steel ball dropped at 50 inches. If it passes that test, you move up to the high mass impact test, which uses a pointed projectile weighing 500 grams, dropped from the same height. And then there is a high velocity impact test — a quarter-inch steel ball traveling at 150 feet per second.

  Some types of work, such as welding, require that the lens filter incoming light. The light can be visible light, or of wavelength
s shorter (ultraviolet) or longer (infrared) than those which we can see. (We will ignore X-rays in this article.)

  OSHA considers ultraviolet radiation to be the most dangerous of the three radiation components, as it can burn the skin, and damage the lens of the eye. Intense visible light can dazzle the welder, resulting in dangerous errors, and retinal damage can be experienced in extreme cases. OSHA considers infrared to be the least dangerous, although it can heat the skin and subcutaneous tissues, resulting in burns.

  The degree to which a filter absorbs visible light is expressed as a shade number. A SN 8 filter blocks 99.9% (all but one thousandth) of the light, while SN 15 blocks all but one-millionth of it. According to MrEclipse.Com, smoked glass has a shade number of 11.6. Its transmittance of infrared was 0.639%, near UV 0.00054%, and farther UV 0.00032%. However, the site warned that it is difficult to produce a nice, thick coating, and that it rubs off easily. In contrast, a standard Welding Filter Shade 12 had a shade number of 11.9, infrared transmittance 0.0049%, near UV .000035%, and further UV .000039%.

  It may be possible for 163x glassworkers to apply a protective surface coating to smoked glass. Another possibility is to produced a strongly colored (perhaps "black") glass.

  What about the other forms of radiation? The good news is that garden variety soda lime glass is going to strongly absorb short wave UV and far infrared light (beyond two microns). The bad news is that, without modern equipment, it isn't easy to measure just how much "invisible" radiation a given piece of glass absorbs.