Safety Tidbit 4.10 – Air Quality

Safety Tidbit 4.10 – Air Quality

What happens if you spill a container of paint stripper with xylene that you bought at Lowes or Home Depot? Alternatively, you applied the paint stripper on your kitchen cabinets that you are refinishing. Let’s do a little “back of the envelope” calculations. Scenario: Determine the final air concentration in ppm in a 18 ft x 25 ft x 9 ft space, say something like your garage . And say the space (garage) nominally has  five air changes per hour (your garage door is open). Assume after 30 minutes, 1-liter or about a quarter of your 1-gallon container of paint stripper spills and evaporates (or, you applied the stripper to your kitchen cabinets). After all, the manufacturer says it evaporates quickly and to use it in a well-ventilated area or outdoors.

We’ll assume that all of the stripper evaporates and diffuses rapidly within the space. However, in practice there will be areas of high concentration and areas of low concentrations based the configuration of the space. Now let’s go through the steps:

·      Determine the room volume in cubic feet (V). Answer - 4.050 ft3 or 114.696 m3

·      Convert the volume of xylene spilled into mass using specific gravity. Answer - 880 grams

·      Determine how many mg/m3 of xylene are in the air (Ci). Answer - 7,672 mg/m3

·      Next, using the Ideal Gas Law and the molecular weight, convert mg/m3 to ppm. Answer - 1770 ppm.

·      Calculate the air flow (Q), given 5 air changes per hour. Answer - 337.5 cfm.

·      Rearrange the steady-state formula and calculate the air concentration (C) after 30 minutes

Steady-state formula = or  C=Ci*〖0.5〗^((T/0.693)*(Q/Vr) )

Answer: 145 ppm

OSHA PEL = 100 ppm

I think a respirator may be in order or better yet engineer out the problem and get a good fan and get more dilution ventilation.

Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan

P.S. If you have a new safety or health question, please let me know.

Safety Tidbit 4.09 - Machine Guarding

Safety Tidbit 4.09 – Machine Guarding

 

Reference:     

I love OSHA’s machine guarding standard. It’s so absolute. 1910.212(a)(3)(ii) reads: “The point of operation of machines whose operation exposes an employee to injury, shall be guarded. The guarding device shall be in conformity with any appropriate standards therefor, or, in the absence of applicable specific standards, shall be so designed and constructed as to prevent the operator from having any part of his body in the danger zone during the operating cycle.” In other words, keep your workers safe, identify the point of operation of your machines and guard them.

The standard has an added benefit to employers. It does not dictate what control they are to use just that they be in conformity with “any appropriate standards.” So, OSHA leaves it up to the discretion of the employer as to what might work best given the employer’s particular circumstances. ANSI helps out a bit here to give some options for the employers to choose from. ANSI says there are guards and devices. A guard is a physical barrier whereas, a device may be a safeguarding device that detects or prevents inadvertent access to a hazard. Or, the device may generate a noticeable (distinctive by sound or intensity) audible or visual signal to warn of an approaching or present hazard. ANSI further describes the use of safe work practices during the following:

·      tasks are complex

·      tasks have high risk;

·      training, skill or work experience is limited;

·      other safeguarding is removed or bypassed;

·      required to augment other safeguarding

To help employers keep their workers safe they can use complimentary equipment such as safety blocks, chain locks, locking pins, work holding equipment, stopping performance monitor. These don’t really get rid of the hazard, but they do help keep unprotected fingers and hands out of harm’s way.

So simply put, protection of the workers is most important. OSHA doesn’t care if the piece of equipment is 100 years old and didn’t come with guards or bought overseas and doesn’t have guarding, the employer must abate the hazard. But hey, they can use their imagination and design something that works well.

Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan

P.S. If you have a new safety or health question, please let me know.

Safety Tidbit 4.08 - Silica Enforcement

Safety Tidbit 4.08 – Silica Enforcement

 

Reference:      Interim Enforcement Guidance June 25, 2018

I was working on a homework project for my IH students. The topic is silica. I have been presenting on Silica to the Mid-Atlantic Masonry Association since OSHA passed its new Respirable Crystalline Silica standard. My emphasis has been to teach the mason, hardscapers, ready-mix operators, and precast/architectural plant owners how to formulate their exposure control plan for the operations.

I start each class asking how many of them currently have workers in respiratory protection and the follow-on question who likes to wear a respirator all day?  Usually I quite a few hands of companies that are using respirators, but no one ever says they like to wear a respirator (even for short periods of time). I use this as a hook because if they perform the risk assessment in their plant and create a good exposure control plan they will find that they don’t need to use respirators after some very reasonable process modifications.

Creating an exposure control plan uses the hierarchy of controls but also requires the employer to review all their potential exposure to silica. The hierarchy of control is the process of the eliminating a hazard by using a decreasing less effective protective measures. First, try to eliminate the hazard all together.  Second, substituting the hazardous substance for something less hazardous. Third, engineering out the hazard, traditionally, by using ventilation or wetting the dust, Fourth, administratively controlling the hazard through work practices. And lastly, having the worker wear personal protective equipment (PPE) or in our case respirators to protect themselves.

By systematically profiling the workplace, the employer learns where their worst exposures can occur and take steps to reduce the emissions. I have employers that are worried about controlling exposures to tasks that occur infrequently and for short durations (less than 10 minutes) and miss the bigger exposure that affects more workers.

I never really thought that an employer, giving respirators to workers, was really protecting the workers. More, they were giving the employee the means to protect themselves. Personal protective equipment protects only as well as it is put on and that means the worker is the ultimate decider of the effectiveness of the respirator since they are ones putting it on.

So how does this relate to OSHA enforcement and the silica standard? I was reviewing the new enforcement document for silica that OSHA published during the summer. In the document, the first item a compliance officer is to ask the employer for during an inspection is the see their Exposure Control Plan. So, all that we teach about hazard recognition, evaluation and control is the basis of the Exposure Control Plan. The biggest difference for the silica is that it’s required for any potential exposure versus in the Lead Standard it’s required after exposures reach the permissible exposure limit.

Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan

P.S. If you have a new safety or health question, please let me know.

Safety Tidbit 4.07 - Mold

Safety Tidbit 4.07 – Mold

 

Reference:      OSHA Mold Hazards Disaster Cleanup

Okay, enough with the waterworks already. I am so tired of rain. As a homeowner, with rain comes the chance of water coming into my home where I don’t want it. Mold is a type of fungi as you well know. Most molds reproduce by forming spores which are released into the air. When spores land on a suitable moist surface they begin to grow, can penetrate porous materials (e.g., carpeting, drywall, wood, in other words, pretty much most things in our homes) and release chemicals. Most molds are harmless. However, some can cause infections, allergy symptoms and produce toxins. But let’s not forget that we need molds and fungi to breakdown all the leaves that are falling outside.

What do you do when the water brings mold into your home, and it takes over? The first rule in mold cleanup is to control the source of moisture. Drying can involve the use of fans, blowers and/or dehumidifiers. However, the more humid the air, the less effective the blowers will be. It is often more cost-effective to remove and replace the building materials than to dry and clean mold-contaminated materials.

While cleaning up mold affected areas use engineering controls, work practices, and personal protective equipment (PPE). Sounds a bit like the use of the hierarchy of controls (e.g., Elimination, Substitution, Engineering Controls, Warnings, Administrative Controls, Personal Protective Equipment). Inhalation is the route of exposure of most concern to cleanup workers. OSHA gives a few suggestions:

Engineering Controls

•       Re-wetting materials with a mist of water to suppress spores, dust and debris.

•       Wrap and seal the items that will be discarded in plastic bags or sheets to reduce the spread of spores.

•       Provide natural or local exhaust ventilation during all cleaning steps.

Work Practices

•       Avoid breathing dust.

•       After an area has been cleaned and is completely dry, vacuum the area with a HEPA vacuum.

•       HEPA vacuums are also recommended for cleaning up dust that may have settled on surfaces outside the work area.

•        

I’m a little confused though, OSHA has a very generic work practice to “avoid breathing dust” (are we to hold our breath?).  I like that they recommend moistening the affected areas during remediation to avoid creating dust. Also, putting debris in sealed or plastic bags makes good sense. All of their recommendations are examples of good old-fashioned industrial hygiene practices and engineer out the hazard if possible (wet it and/or vacuum it).

Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan

P.S. If you have an interesting safety or health question please let me know.