Safety Tidbit #29 – Noise Thresholds

Safety Tidbit #29 – Noise Thresholds

This week I was conducting some noise dosimetry.  I like dosimetry over just taking noise readings as the dosimeter goes wherever the worker goes and evaluates the sound pressure reading every minute.  Much more efficient than me lingering around using a handheld meter and trying to get a reading in the “hearing zone” of the worker.  So I find using the dosimeter a much more elegant solution.  Now if I am trying to pinpoint a noise source or even better getting a profile of the source so I can reduce the noise levels, then my handy-dandy meter is my best friend. Especially when the meter can split out the octaves.  But I digress. What I wanted to discuss today, although it will be a brief discussion, is the time-weighted averages we hear (no pun intended) so much about. 

Most of us know of OSHA’s 8-hour Permissible Exposure Limit (PEL) for noise which equals 90 decibels (on the A-weighted scale, again let’s not delve into what is dBA just now).  But OSHA also has the medical surveillance action level (AL) of 85 dBA.  Unfortunately, these two values are not quite apples and apples because OSHA dictates the parameters we must use to evaluate the workplace for each.  We use a dosimeter to help us evaluate however we have to program the equipment to look at the right noise and perform the correct calculations.  That’s where the parameters come in.  Since the Walsh-Healy Act, for the PEL, OSHA says to use a threshold of 90 dBA, capture everything between 90 and 140 dBA and use a five dBA excursion limit.  Then in 1982, Hearing Conservation Programs became all the rage and OSHA said to be more protective we want you also to evaluate noise between 80 and 130 dBA with a threshold of 80 dBA, and we will keep the excursion limit at five dBA.  We will not talk about the excursion limit today.

The threshold, 90 dBA for the PEL and 80 for the AL, what this parameter does, tells the dosimeter to ignore any sound levels that do not meet the threshold.  For instance, if I use my trusty handheld meter I find the noise level on the floor to be 88 dBA.  The dosimeter calculating for the AL will record this reading and add to the noise dose for the worker.  However, the dosimeter calculating for the PEL will ignore the level and not add to the noise dose for the PEL.  As you might guess a fair amount of noise may be overlooked when only evaluating for the PEL.  As a consultant, I wish to advise my client as well as I am able.  I usually don’t worry about evaluating the PEL since if they are protecting the worker starting at the AL, then the client is much more protective.  Saying that, if my dosimeter's reading comes back and the 8-hour time-weighted average exceeds 90 dBA the client must look to reduce the occupational exposure to noise, and I get out my trusty handheld meter or better yet my octave band analyzer and have some fun! Oh, and by the way, this is just OSHA’s take on noise and is quite old.  NIOSH and really everyone else sets the threshold for whatever is the limit of the equipment. 

I hope this was helpful. As usual, if you have comments or if you have a particular topic you wish me to discuss, please let me know.  Thanks for reading!

Safety Tidbit #28 – Propane Forklifts and Carbon Monoxide

Safety Tidbit #28 – Propane Forklifts and Carbon Monoxide

I like what I do for a living. I get to go to all these neat small employers and watch what they do to hurt themselves. I mean to earn a living. Sorry.  Recently, I was touring a facility, and I noticed a forklift moving pallets of electronics materials around.  The driver was very conscientious about putting his seatbelt on (at least he made sure I saw that he did).  As I continued to walk along, I noticed a couple of workers open a set of double man-doors to allow the forklift operator to pass through with a pallet of electronics materials into a room on the other side.  This building is a large (approx. 100,000 square feet and 25 feet high) concrete slab; metal I-beam framed, and metal-sided structure.  Nothing unusual, these commercial and industrial buildings are all over the place. They will typically have one side of the building with windows overlooking the parking lot for the management, admin, and engineering staff and the rest of the facility is a vast open area tailored to the needs of the company.  This particular company had a series of smaller specialty shops lining one other wall for supply, maintenance, and electronics repair (which is where I wanted to head).

After a short time, our tour entered the electronics repair room where I found a much smaller (20 by 30 space) cluttered with electronics “stuff” as is their custom. I don’t think these guys ever throw anything away.  There was one man-door as an exit to the outside.  However, since there was so much clutter in the space they were having a difficult time deciding where exactly to put the new pallet of “stuff.”  Consequently, when I entered the room, the forklift was still running.  Unfortunately, the use propane forklifts throughout the facility and the emissions coming from the lift were quite noticeable when I entered the room.  The workers pointed to the small ceiling fan 25 feet up in the air when I asked about ventilation.  I promptly inquired about a Safety Data Sheet on the propane to use it as a teaching aide.  My first question was: is carbon monoxide (a combustion by-product) of propane lighter or heavier than air? They all said lighter as the gas coming out is heated.  True but how long do you think the emissions are going to stay heated? Long enough to get all of the ways up to the fan?  And even if the fan was pulling the air up do you think it would be able to pull the carbon monoxide all the way from the floor up? By the way, the fan was going to pull anything since it was turning the wrong direction and was pushing what little air it was moving downwards. 

Ultimately, the answer is that carbon monoxide and air are about the same density.  Furthermore, most of us know that carbon monoxide is deadly.  Therefore, I recommended increased ventilation (open the doors and get some pedestal fans). The fans will help move the emissions around, and the open doors will keep fresh air coming into the space.  Ultimately, I would like to see them use an electric forklift or even a man-powered pallet jack as the electronics repair space is quite small and congested with “stuff” and I see someone getting struck-by the forklift eventually.

Hope you found this informative a little entertaining. Thanks for reading!

Safety Tidbit #27 - Trenching: Competent Person

Safety Tidbit #27 - Trenching: Competent Person

I was on a construction job site recently and the first question I asked - who is the competent person at the site?  This is usually my first question since the qualified person has the responsibility to make most of the decisions on the site and, therefore, is directly responsible for the lives and safety of all of the workers on that site.  On this site, a young man, who happened to be the company owner’s son, raised his hand. He appeared to have very little training or experience and this site had a very mean looking trench.  Which was why I stopped to begin with!

First, what is a competent person?  OSHA defines a competent person as:

A person who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has the authorization to take prompt corrective measures to eliminate them.

In our particular case competent translates to the following knowledge:

1) Training, experience, and knowledge of:

a) Soil analysis;

b) Use of protective systems; and

c) Requirements of 29CFR1926 Subpart P

2) Ability to detect:

a) Conditions that could result in cave-ins;

b)    Failures in protective systems;

c)    Hazardous atmospheres; and

d)    Other hazards including those associated with confined spaces.

3) And above all - authority to take prompt corrective measures to eliminate existing and predictable hazards and to stop work when required.

Just because the “competent person” on our site was young did not mean he couldn’t be a competent person. Ultimately, I didn’t want to appear prejudiced so; I proceeded with a few simple trench-related questions. First, what was the depth of the trench - he could not answer.  Second, what type of soil was present - no answer.  Third, what protective system were they using - dead air.  Fourth was an easy one, did he know the requirements of 29CFR1926 Subpart P - success!! He said he remembered hearing about it during the OSHA 10-hour course that he and the whole crew attended just before starting this job.  I did give him a little credit, however, since he was the owner’s son he probably had Item C above covered.

Remember: A competent person has a great deal of responsibility and must be given as many tools as possible to perform their job so they can make informed decisions and ensure all workers go home each and every day.

BTW: The trench was 12 feet deep 4 feet wide, it had rained the night before and water was standing in the bottom of the trench and pouring in from the sides. And, oh, there was no trench box or shoring material to be seen anywhere. Upside - They quit for the day.